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Lasers
Lecture
25-03-2020
Semiconductor lasers
2
bull Semiconductors play an important role in optoelectronics as sources (LEDs lasers) and photodetectors
bull Semiconductor lasers are the most numerous of all lasers
bull Widespread applications optical fiber communications barcode scanners laser printers compact disc players pumps for other types of lasers etc hellip
bull Many valuable properties
ndash High efficiency (EO) typically 30-50
ndash Very small size (micrometers millimeters)
ndash Mostly electrical pumping require very modest power supplies also optical pumping
ndash Low voltages (few volts) currents from mA to tens of A
ndash High modulation frequencies (up to 20 GHz)
ndash Many different wavelengths available (from VIS to IRMIR)
ndash Good beam quality possible
bull Ideal lasers Why do we need other lasers
Semiconductor lasers
3
Semiconductors
ldquoBonding in Metals and Semiconductorsrdquo section 126 Principles of General Chemistry (v 10)
Conduction band
Valence band
4
Semiconductors
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
5
Semiconductors
conduction band
valence band
E
k
Eg
2 2 2
0 02 2
p kE
m m
The allowed kinetic energies of an electron
p ndash particle momentum
m0 ndash effective mass of the electron
k ndash wave vector
h ndash Planck constant
6
Direct indirect bandgap In order to achieve electroluminescence it is necessary to select an appropriate
semiconductors material The most useful material for this purpose are so-called
DIRECT BANDGAP SEMICONDUCTORS
Direct bandgap semiconductors Indirect bandgap semiconductors
electron photon
or momentum p = 2πhk
valence band
wave vector k
conduction band
conduction band
k p = 2πhk
7
Intrinsic semiconductor An intrinsic semiconductor is one that contains relatively small amounts of
impurities At finite temperatures determines the excitation of electrons from the
valence band to the conduction band and levels an equal number of holes in the
valence band
The electron density n(E) (number of electrons per unit volume) in an
semiconductor is given by
toptop EE
dEEFENdEEnn )()()(
where N(E) - density of allowed energy states per unit volume
Etop - the top of the conduction band Etop
kTEE FeEF
)(1
1)(
k ndash the Boltzman constant
T ndash the absolute temperature
- Fermi-Dirac
distribution function
8
Fermi level
kTEE FeEF
)(1
1)(
- Fermi-Dirac
distribution function
Fermi energy (EF) ndash is that energy value for which the probability of the state
being occupied is frac12
At T = 0 all energy states below EF are completely filled and above EF are
completely empty
Concentration of the electrons in the conduction band
32
( )
2
22 FE E kTe
e
m kTn e
h
Concentration increases when EF moves closer to conduction band
9
Intrinsic semiconductor
FERMI DISTRIBUTION F(E)
VERSUS (E ndash EF ) FOR
VARIOUS TEMPERATURES
The Fermi distribution function can be approximated by simpler expressions
kTEEforeEF F
kTEE F 3)(
kTEEforeEF F
kTEE F 31)(
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
10
Intrinsic semiconductor
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
(a) band
diagram
(b) density
of state (c) fermi
distribution
function
(d) Carrier
concentration
11
Doping bull The energy band
structure may be
modified by introducing
impurity atoms to the
crystal lattice (doping)
bull Eg silicon group IV
from the periodic table
4 outer electrons
bull Donor impurity atom
from the V group (eg
nitrogen phosphorus)
with 5 outer electrons ndash
the one free electron can
be easily lost to the
conduction band
bull Acceptor impurity
atom from the III group
(eg boron) ndash three outer
electrons contributes a
hole to the valence band We can modify the Fermi level by doping
12
p-n junction E
nerg
y
Ec
EV
Ec
EV
Ec
EV
EF EF
EF
p n
eV0
EF
p n
+
+
+
+
-
-
-
-
Energ
y
13
Semiconductors Part of the Periodic Table Related to Semiconductors
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
14
Semiconductors Typical compounds
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
15
Electroluminescence (LED)
16
p-n junction laser (homojunction)
Taken from [4] JT Verdeyen Laser Electronics Prentice Hall Englewood Cliffs 1995
Edge-emitting laser
17
Typical semiconductor laser
The ideal output power
against current
characteristic
Taken from [11] JM Senior Optical Fiber Communications Prentice Hall New York 1992
18
Threshold gaincurrent
Lets introduce threshold gain coefficient thg
depending on current density
threshold
thth Jg
where β is a constant appropriate to specific devices
Fractional loss Fl of the Fabry ndashPerot cavity is
LRRloss
2exp21
where
- single loss coefficient per unit round trip
Fractional gain of the Fabry ndashPerot cavity is
Lggain
2exp
where g
- single gain coefficient per unit round trip
19
Threshold gaincurrent The threshold case requires
12exp2exp 21 LRRLg
12exp21 LgRR
Hence
21
1ln
2
1
RRLg th
the gain threshold
So we can write
thth Jg
by transformation we can find the threshold value for current density
21
1ln
2
11
RRLJ th
20
Threshold gaincurrent Example
A GaAs injection laser has an optical cavity of length L = 250 μm and widh
w = 100 μm At normal operating temperature the gain factor
β = 21 10-3 [Acm-3] and the loss coefficient
= 10 refractive index n = 36
Assuming R1 = 1 and reflection of mirror 2 3201
12
2
n
nR
The threshold current may be obtain from the equation from the previous slide
2
3
21
106521
ln2
11
cm
A
RRLJ th
The threshold current
mAcavityopticaltheofareaJI thth 663
Taken from [11] JM Senior Optical Fiber Communications Prentice Hall New York 1992
21
Efficiency
Below the threshold laser acts like a LED
Above the threshold stimulated emission
dominates the spontaneous emission
causing laser emission
Formal definition of the efficiency η
For a laser with drive current I and a threshold
current Ithr the output power of the laser at
wavelength λ is
( )thr
hcP I I
e
22
bull More efficient diode lasers are based on heterojunctions
bull Heterojunction is formed between two different semiconductors with different bangap energies
bull Typical materials eg GaAs and AlGaAs
bull One semiconductor is sandwiched between two cladding layers of another semiconductor
Heterojunction lasers
23
Heterojunction laser
AlGaAs (n)
GaAs
Substrate n (GaAs)
AlGaAs (p) 1 μm
1 μm
015 μm
24
LED vs Laser diode
Power vs Current Spectral width
25
Materials amp wavelengths
Taken from Optics and Photonics an introduction 2nd edition Wiley
26
bull Fabry-Perot
bull Distributed Feedback (DFB)
bull Distributed Bragg Reflector (DBR)
bull Grating-stabilized laser
bull External cavity laser (ECL)
Cavities
27
Modes
Taken from [9] F Tragger Ed Springer Handbook of Lasers and Optics Springer New York 2007
28
bull Incorporates the grating within the laser diode structure itself
bull The Bragg grating selects only one mode
bull single-frequency operation over broad temperature and current ranges
bull Tuning 2-4 nm
bull Linewidth 1 ndash 10 MHz
Distributed feedback laser
29
bull The reflector is outsite the active section
bull Broad tuning range possible (up to 40 nm)
bull Mode hopping possible
Distributed Bragg Reflector
30
bull The grating stabilizes the wavelength of the laser (provides a small feedback)
bull Grating is outside the laser (it is not a laser mirror)
bull Might be placed on a fiber
Grating-stabilized lasers
31
External cavity lasers
bull A grating inside allows
wavelength tuning in a
broad range
bull The linewidths are very
narrow
bull bdquoBulkrdquo construction long
resonator
32
bull VCSEL
Surface emitting laser
bull Limited output power
bull Very small resonator
length (few micrometers)
bull Easy achievable single-
frequency operation
bull High modulation
frequency (useful in
telecom)
bull Most common emission
750 ndash 980 nm
33
bull VECSEL (Vertical External-cavity Surface-emitting Laser)
External cavity
34
VECSELs VECSELs enable optical pumping
35
bull TO can
Housings
36
bull C-mount
Housings
37
bull 14-pin Butterfly
Housings
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
2
bull Semiconductors play an important role in optoelectronics as sources (LEDs lasers) and photodetectors
bull Semiconductor lasers are the most numerous of all lasers
bull Widespread applications optical fiber communications barcode scanners laser printers compact disc players pumps for other types of lasers etc hellip
bull Many valuable properties
ndash High efficiency (EO) typically 30-50
ndash Very small size (micrometers millimeters)
ndash Mostly electrical pumping require very modest power supplies also optical pumping
ndash Low voltages (few volts) currents from mA to tens of A
ndash High modulation frequencies (up to 20 GHz)
ndash Many different wavelengths available (from VIS to IRMIR)
ndash Good beam quality possible
bull Ideal lasers Why do we need other lasers
Semiconductor lasers
3
Semiconductors
ldquoBonding in Metals and Semiconductorsrdquo section 126 Principles of General Chemistry (v 10)
Conduction band
Valence band
4
Semiconductors
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
5
Semiconductors
conduction band
valence band
E
k
Eg
2 2 2
0 02 2
p kE
m m
The allowed kinetic energies of an electron
p ndash particle momentum
m0 ndash effective mass of the electron
k ndash wave vector
h ndash Planck constant
6
Direct indirect bandgap In order to achieve electroluminescence it is necessary to select an appropriate
semiconductors material The most useful material for this purpose are so-called
DIRECT BANDGAP SEMICONDUCTORS
Direct bandgap semiconductors Indirect bandgap semiconductors
electron photon
or momentum p = 2πhk
valence band
wave vector k
conduction band
conduction band
k p = 2πhk
7
Intrinsic semiconductor An intrinsic semiconductor is one that contains relatively small amounts of
impurities At finite temperatures determines the excitation of electrons from the
valence band to the conduction band and levels an equal number of holes in the
valence band
The electron density n(E) (number of electrons per unit volume) in an
semiconductor is given by
toptop EE
dEEFENdEEnn )()()(
where N(E) - density of allowed energy states per unit volume
Etop - the top of the conduction band Etop
kTEE FeEF
)(1
1)(
k ndash the Boltzman constant
T ndash the absolute temperature
- Fermi-Dirac
distribution function
8
Fermi level
kTEE FeEF
)(1
1)(
- Fermi-Dirac
distribution function
Fermi energy (EF) ndash is that energy value for which the probability of the state
being occupied is frac12
At T = 0 all energy states below EF are completely filled and above EF are
completely empty
Concentration of the electrons in the conduction band
32
( )
2
22 FE E kTe
e
m kTn e
h
Concentration increases when EF moves closer to conduction band
9
Intrinsic semiconductor
FERMI DISTRIBUTION F(E)
VERSUS (E ndash EF ) FOR
VARIOUS TEMPERATURES
The Fermi distribution function can be approximated by simpler expressions
kTEEforeEF F
kTEE F 3)(
kTEEforeEF F
kTEE F 31)(
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
10
Intrinsic semiconductor
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
(a) band
diagram
(b) density
of state (c) fermi
distribution
function
(d) Carrier
concentration
11
Doping bull The energy band
structure may be
modified by introducing
impurity atoms to the
crystal lattice (doping)
bull Eg silicon group IV
from the periodic table
4 outer electrons
bull Donor impurity atom
from the V group (eg
nitrogen phosphorus)
with 5 outer electrons ndash
the one free electron can
be easily lost to the
conduction band
bull Acceptor impurity
atom from the III group
(eg boron) ndash three outer
electrons contributes a
hole to the valence band We can modify the Fermi level by doping
12
p-n junction E
nerg
y
Ec
EV
Ec
EV
Ec
EV
EF EF
EF
p n
eV0
EF
p n
+
+
+
+
-
-
-
-
Energ
y
13
Semiconductors Part of the Periodic Table Related to Semiconductors
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
14
Semiconductors Typical compounds
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
15
Electroluminescence (LED)
16
p-n junction laser (homojunction)
Taken from [4] JT Verdeyen Laser Electronics Prentice Hall Englewood Cliffs 1995
Edge-emitting laser
17
Typical semiconductor laser
The ideal output power
against current
characteristic
Taken from [11] JM Senior Optical Fiber Communications Prentice Hall New York 1992
18
Threshold gaincurrent
Lets introduce threshold gain coefficient thg
depending on current density
threshold
thth Jg
where β is a constant appropriate to specific devices
Fractional loss Fl of the Fabry ndashPerot cavity is
LRRloss
2exp21
where
- single loss coefficient per unit round trip
Fractional gain of the Fabry ndashPerot cavity is
Lggain
2exp
where g
- single gain coefficient per unit round trip
19
Threshold gaincurrent The threshold case requires
12exp2exp 21 LRRLg
12exp21 LgRR
Hence
21
1ln
2
1
RRLg th
the gain threshold
So we can write
thth Jg
by transformation we can find the threshold value for current density
21
1ln
2
11
RRLJ th
20
Threshold gaincurrent Example
A GaAs injection laser has an optical cavity of length L = 250 μm and widh
w = 100 μm At normal operating temperature the gain factor
β = 21 10-3 [Acm-3] and the loss coefficient
= 10 refractive index n = 36
Assuming R1 = 1 and reflection of mirror 2 3201
12
2
n
nR
The threshold current may be obtain from the equation from the previous slide
2
3
21
106521
ln2
11
cm
A
RRLJ th
The threshold current
mAcavityopticaltheofareaJI thth 663
Taken from [11] JM Senior Optical Fiber Communications Prentice Hall New York 1992
21
Efficiency
Below the threshold laser acts like a LED
Above the threshold stimulated emission
dominates the spontaneous emission
causing laser emission
Formal definition of the efficiency η
For a laser with drive current I and a threshold
current Ithr the output power of the laser at
wavelength λ is
( )thr
hcP I I
e
22
bull More efficient diode lasers are based on heterojunctions
bull Heterojunction is formed between two different semiconductors with different bangap energies
bull Typical materials eg GaAs and AlGaAs
bull One semiconductor is sandwiched between two cladding layers of another semiconductor
Heterojunction lasers
23
Heterojunction laser
AlGaAs (n)
GaAs
Substrate n (GaAs)
AlGaAs (p) 1 μm
1 μm
015 μm
24
LED vs Laser diode
Power vs Current Spectral width
25
Materials amp wavelengths
Taken from Optics and Photonics an introduction 2nd edition Wiley
26
bull Fabry-Perot
bull Distributed Feedback (DFB)
bull Distributed Bragg Reflector (DBR)
bull Grating-stabilized laser
bull External cavity laser (ECL)
Cavities
27
Modes
Taken from [9] F Tragger Ed Springer Handbook of Lasers and Optics Springer New York 2007
28
bull Incorporates the grating within the laser diode structure itself
bull The Bragg grating selects only one mode
bull single-frequency operation over broad temperature and current ranges
bull Tuning 2-4 nm
bull Linewidth 1 ndash 10 MHz
Distributed feedback laser
29
bull The reflector is outsite the active section
bull Broad tuning range possible (up to 40 nm)
bull Mode hopping possible
Distributed Bragg Reflector
30
bull The grating stabilizes the wavelength of the laser (provides a small feedback)
bull Grating is outside the laser (it is not a laser mirror)
bull Might be placed on a fiber
Grating-stabilized lasers
31
External cavity lasers
bull A grating inside allows
wavelength tuning in a
broad range
bull The linewidths are very
narrow
bull bdquoBulkrdquo construction long
resonator
32
bull VCSEL
Surface emitting laser
bull Limited output power
bull Very small resonator
length (few micrometers)
bull Easy achievable single-
frequency operation
bull High modulation
frequency (useful in
telecom)
bull Most common emission
750 ndash 980 nm
33
bull VECSEL (Vertical External-cavity Surface-emitting Laser)
External cavity
34
VECSELs VECSELs enable optical pumping
35
bull TO can
Housings
36
bull C-mount
Housings
37
bull 14-pin Butterfly
Housings
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
3
Semiconductors
ldquoBonding in Metals and Semiconductorsrdquo section 126 Principles of General Chemistry (v 10)
Conduction band
Valence band
4
Semiconductors
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
5
Semiconductors
conduction band
valence band
E
k
Eg
2 2 2
0 02 2
p kE
m m
The allowed kinetic energies of an electron
p ndash particle momentum
m0 ndash effective mass of the electron
k ndash wave vector
h ndash Planck constant
6
Direct indirect bandgap In order to achieve electroluminescence it is necessary to select an appropriate
semiconductors material The most useful material for this purpose are so-called
DIRECT BANDGAP SEMICONDUCTORS
Direct bandgap semiconductors Indirect bandgap semiconductors
electron photon
or momentum p = 2πhk
valence band
wave vector k
conduction band
conduction band
k p = 2πhk
7
Intrinsic semiconductor An intrinsic semiconductor is one that contains relatively small amounts of
impurities At finite temperatures determines the excitation of electrons from the
valence band to the conduction band and levels an equal number of holes in the
valence band
The electron density n(E) (number of electrons per unit volume) in an
semiconductor is given by
toptop EE
dEEFENdEEnn )()()(
where N(E) - density of allowed energy states per unit volume
Etop - the top of the conduction band Etop
kTEE FeEF
)(1
1)(
k ndash the Boltzman constant
T ndash the absolute temperature
- Fermi-Dirac
distribution function
8
Fermi level
kTEE FeEF
)(1
1)(
- Fermi-Dirac
distribution function
Fermi energy (EF) ndash is that energy value for which the probability of the state
being occupied is frac12
At T = 0 all energy states below EF are completely filled and above EF are
completely empty
Concentration of the electrons in the conduction band
32
( )
2
22 FE E kTe
e
m kTn e
h
Concentration increases when EF moves closer to conduction band
9
Intrinsic semiconductor
FERMI DISTRIBUTION F(E)
VERSUS (E ndash EF ) FOR
VARIOUS TEMPERATURES
The Fermi distribution function can be approximated by simpler expressions
kTEEforeEF F
kTEE F 3)(
kTEEforeEF F
kTEE F 31)(
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
10
Intrinsic semiconductor
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
(a) band
diagram
(b) density
of state (c) fermi
distribution
function
(d) Carrier
concentration
11
Doping bull The energy band
structure may be
modified by introducing
impurity atoms to the
crystal lattice (doping)
bull Eg silicon group IV
from the periodic table
4 outer electrons
bull Donor impurity atom
from the V group (eg
nitrogen phosphorus)
with 5 outer electrons ndash
the one free electron can
be easily lost to the
conduction band
bull Acceptor impurity
atom from the III group
(eg boron) ndash three outer
electrons contributes a
hole to the valence band We can modify the Fermi level by doping
12
p-n junction E
nerg
y
Ec
EV
Ec
EV
Ec
EV
EF EF
EF
p n
eV0
EF
p n
+
+
+
+
-
-
-
-
Energ
y
13
Semiconductors Part of the Periodic Table Related to Semiconductors
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
14
Semiconductors Typical compounds
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
15
Electroluminescence (LED)
16
p-n junction laser (homojunction)
Taken from [4] JT Verdeyen Laser Electronics Prentice Hall Englewood Cliffs 1995
Edge-emitting laser
17
Typical semiconductor laser
The ideal output power
against current
characteristic
Taken from [11] JM Senior Optical Fiber Communications Prentice Hall New York 1992
18
Threshold gaincurrent
Lets introduce threshold gain coefficient thg
depending on current density
threshold
thth Jg
where β is a constant appropriate to specific devices
Fractional loss Fl of the Fabry ndashPerot cavity is
LRRloss
2exp21
where
- single loss coefficient per unit round trip
Fractional gain of the Fabry ndashPerot cavity is
Lggain
2exp
where g
- single gain coefficient per unit round trip
19
Threshold gaincurrent The threshold case requires
12exp2exp 21 LRRLg
12exp21 LgRR
Hence
21
1ln
2
1
RRLg th
the gain threshold
So we can write
thth Jg
by transformation we can find the threshold value for current density
21
1ln
2
11
RRLJ th
20
Threshold gaincurrent Example
A GaAs injection laser has an optical cavity of length L = 250 μm and widh
w = 100 μm At normal operating temperature the gain factor
β = 21 10-3 [Acm-3] and the loss coefficient
= 10 refractive index n = 36
Assuming R1 = 1 and reflection of mirror 2 3201
12
2
n
nR
The threshold current may be obtain from the equation from the previous slide
2
3
21
106521
ln2
11
cm
A
RRLJ th
The threshold current
mAcavityopticaltheofareaJI thth 663
Taken from [11] JM Senior Optical Fiber Communications Prentice Hall New York 1992
21
Efficiency
Below the threshold laser acts like a LED
Above the threshold stimulated emission
dominates the spontaneous emission
causing laser emission
Formal definition of the efficiency η
For a laser with drive current I and a threshold
current Ithr the output power of the laser at
wavelength λ is
( )thr
hcP I I
e
22
bull More efficient diode lasers are based on heterojunctions
bull Heterojunction is formed between two different semiconductors with different bangap energies
bull Typical materials eg GaAs and AlGaAs
bull One semiconductor is sandwiched between two cladding layers of another semiconductor
Heterojunction lasers
23
Heterojunction laser
AlGaAs (n)
GaAs
Substrate n (GaAs)
AlGaAs (p) 1 μm
1 μm
015 μm
24
LED vs Laser diode
Power vs Current Spectral width
25
Materials amp wavelengths
Taken from Optics and Photonics an introduction 2nd edition Wiley
26
bull Fabry-Perot
bull Distributed Feedback (DFB)
bull Distributed Bragg Reflector (DBR)
bull Grating-stabilized laser
bull External cavity laser (ECL)
Cavities
27
Modes
Taken from [9] F Tragger Ed Springer Handbook of Lasers and Optics Springer New York 2007
28
bull Incorporates the grating within the laser diode structure itself
bull The Bragg grating selects only one mode
bull single-frequency operation over broad temperature and current ranges
bull Tuning 2-4 nm
bull Linewidth 1 ndash 10 MHz
Distributed feedback laser
29
bull The reflector is outsite the active section
bull Broad tuning range possible (up to 40 nm)
bull Mode hopping possible
Distributed Bragg Reflector
30
bull The grating stabilizes the wavelength of the laser (provides a small feedback)
bull Grating is outside the laser (it is not a laser mirror)
bull Might be placed on a fiber
Grating-stabilized lasers
31
External cavity lasers
bull A grating inside allows
wavelength tuning in a
broad range
bull The linewidths are very
narrow
bull bdquoBulkrdquo construction long
resonator
32
bull VCSEL
Surface emitting laser
bull Limited output power
bull Very small resonator
length (few micrometers)
bull Easy achievable single-
frequency operation
bull High modulation
frequency (useful in
telecom)
bull Most common emission
750 ndash 980 nm
33
bull VECSEL (Vertical External-cavity Surface-emitting Laser)
External cavity
34
VECSELs VECSELs enable optical pumping
35
bull TO can
Housings
36
bull C-mount
Housings
37
bull 14-pin Butterfly
Housings
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
4
Semiconductors
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
5
Semiconductors
conduction band
valence band
E
k
Eg
2 2 2
0 02 2
p kE
m m
The allowed kinetic energies of an electron
p ndash particle momentum
m0 ndash effective mass of the electron
k ndash wave vector
h ndash Planck constant
6
Direct indirect bandgap In order to achieve electroluminescence it is necessary to select an appropriate
semiconductors material The most useful material for this purpose are so-called
DIRECT BANDGAP SEMICONDUCTORS
Direct bandgap semiconductors Indirect bandgap semiconductors
electron photon
or momentum p = 2πhk
valence band
wave vector k
conduction band
conduction band
k p = 2πhk
7
Intrinsic semiconductor An intrinsic semiconductor is one that contains relatively small amounts of
impurities At finite temperatures determines the excitation of electrons from the
valence band to the conduction band and levels an equal number of holes in the
valence band
The electron density n(E) (number of electrons per unit volume) in an
semiconductor is given by
toptop EE
dEEFENdEEnn )()()(
where N(E) - density of allowed energy states per unit volume
Etop - the top of the conduction band Etop
kTEE FeEF
)(1
1)(
k ndash the Boltzman constant
T ndash the absolute temperature
- Fermi-Dirac
distribution function
8
Fermi level
kTEE FeEF
)(1
1)(
- Fermi-Dirac
distribution function
Fermi energy (EF) ndash is that energy value for which the probability of the state
being occupied is frac12
At T = 0 all energy states below EF are completely filled and above EF are
completely empty
Concentration of the electrons in the conduction band
32
( )
2
22 FE E kTe
e
m kTn e
h
Concentration increases when EF moves closer to conduction band
9
Intrinsic semiconductor
FERMI DISTRIBUTION F(E)
VERSUS (E ndash EF ) FOR
VARIOUS TEMPERATURES
The Fermi distribution function can be approximated by simpler expressions
kTEEforeEF F
kTEE F 3)(
kTEEforeEF F
kTEE F 31)(
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
10
Intrinsic semiconductor
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
(a) band
diagram
(b) density
of state (c) fermi
distribution
function
(d) Carrier
concentration
11
Doping bull The energy band
structure may be
modified by introducing
impurity atoms to the
crystal lattice (doping)
bull Eg silicon group IV
from the periodic table
4 outer electrons
bull Donor impurity atom
from the V group (eg
nitrogen phosphorus)
with 5 outer electrons ndash
the one free electron can
be easily lost to the
conduction band
bull Acceptor impurity
atom from the III group
(eg boron) ndash three outer
electrons contributes a
hole to the valence band We can modify the Fermi level by doping
12
p-n junction E
nerg
y
Ec
EV
Ec
EV
Ec
EV
EF EF
EF
p n
eV0
EF
p n
+
+
+
+
-
-
-
-
Energ
y
13
Semiconductors Part of the Periodic Table Related to Semiconductors
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
14
Semiconductors Typical compounds
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
15
Electroluminescence (LED)
16
p-n junction laser (homojunction)
Taken from [4] JT Verdeyen Laser Electronics Prentice Hall Englewood Cliffs 1995
Edge-emitting laser
17
Typical semiconductor laser
The ideal output power
against current
characteristic
Taken from [11] JM Senior Optical Fiber Communications Prentice Hall New York 1992
18
Threshold gaincurrent
Lets introduce threshold gain coefficient thg
depending on current density
threshold
thth Jg
where β is a constant appropriate to specific devices
Fractional loss Fl of the Fabry ndashPerot cavity is
LRRloss
2exp21
where
- single loss coefficient per unit round trip
Fractional gain of the Fabry ndashPerot cavity is
Lggain
2exp
where g
- single gain coefficient per unit round trip
19
Threshold gaincurrent The threshold case requires
12exp2exp 21 LRRLg
12exp21 LgRR
Hence
21
1ln
2
1
RRLg th
the gain threshold
So we can write
thth Jg
by transformation we can find the threshold value for current density
21
1ln
2
11
RRLJ th
20
Threshold gaincurrent Example
A GaAs injection laser has an optical cavity of length L = 250 μm and widh
w = 100 μm At normal operating temperature the gain factor
β = 21 10-3 [Acm-3] and the loss coefficient
= 10 refractive index n = 36
Assuming R1 = 1 and reflection of mirror 2 3201
12
2
n
nR
The threshold current may be obtain from the equation from the previous slide
2
3
21
106521
ln2
11
cm
A
RRLJ th
The threshold current
mAcavityopticaltheofareaJI thth 663
Taken from [11] JM Senior Optical Fiber Communications Prentice Hall New York 1992
21
Efficiency
Below the threshold laser acts like a LED
Above the threshold stimulated emission
dominates the spontaneous emission
causing laser emission
Formal definition of the efficiency η
For a laser with drive current I and a threshold
current Ithr the output power of the laser at
wavelength λ is
( )thr
hcP I I
e
22
bull More efficient diode lasers are based on heterojunctions
bull Heterojunction is formed between two different semiconductors with different bangap energies
bull Typical materials eg GaAs and AlGaAs
bull One semiconductor is sandwiched between two cladding layers of another semiconductor
Heterojunction lasers
23
Heterojunction laser
AlGaAs (n)
GaAs
Substrate n (GaAs)
AlGaAs (p) 1 μm
1 μm
015 μm
24
LED vs Laser diode
Power vs Current Spectral width
25
Materials amp wavelengths
Taken from Optics and Photonics an introduction 2nd edition Wiley
26
bull Fabry-Perot
bull Distributed Feedback (DFB)
bull Distributed Bragg Reflector (DBR)
bull Grating-stabilized laser
bull External cavity laser (ECL)
Cavities
27
Modes
Taken from [9] F Tragger Ed Springer Handbook of Lasers and Optics Springer New York 2007
28
bull Incorporates the grating within the laser diode structure itself
bull The Bragg grating selects only one mode
bull single-frequency operation over broad temperature and current ranges
bull Tuning 2-4 nm
bull Linewidth 1 ndash 10 MHz
Distributed feedback laser
29
bull The reflector is outsite the active section
bull Broad tuning range possible (up to 40 nm)
bull Mode hopping possible
Distributed Bragg Reflector
30
bull The grating stabilizes the wavelength of the laser (provides a small feedback)
bull Grating is outside the laser (it is not a laser mirror)
bull Might be placed on a fiber
Grating-stabilized lasers
31
External cavity lasers
bull A grating inside allows
wavelength tuning in a
broad range
bull The linewidths are very
narrow
bull bdquoBulkrdquo construction long
resonator
32
bull VCSEL
Surface emitting laser
bull Limited output power
bull Very small resonator
length (few micrometers)
bull Easy achievable single-
frequency operation
bull High modulation
frequency (useful in
telecom)
bull Most common emission
750 ndash 980 nm
33
bull VECSEL (Vertical External-cavity Surface-emitting Laser)
External cavity
34
VECSELs VECSELs enable optical pumping
35
bull TO can
Housings
36
bull C-mount
Housings
37
bull 14-pin Butterfly
Housings
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
5
Semiconductors
conduction band
valence band
E
k
Eg
2 2 2
0 02 2
p kE
m m
The allowed kinetic energies of an electron
p ndash particle momentum
m0 ndash effective mass of the electron
k ndash wave vector
h ndash Planck constant
6
Direct indirect bandgap In order to achieve electroluminescence it is necessary to select an appropriate
semiconductors material The most useful material for this purpose are so-called
DIRECT BANDGAP SEMICONDUCTORS
Direct bandgap semiconductors Indirect bandgap semiconductors
electron photon
or momentum p = 2πhk
valence band
wave vector k
conduction band
conduction band
k p = 2πhk
7
Intrinsic semiconductor An intrinsic semiconductor is one that contains relatively small amounts of
impurities At finite temperatures determines the excitation of electrons from the
valence band to the conduction band and levels an equal number of holes in the
valence band
The electron density n(E) (number of electrons per unit volume) in an
semiconductor is given by
toptop EE
dEEFENdEEnn )()()(
where N(E) - density of allowed energy states per unit volume
Etop - the top of the conduction band Etop
kTEE FeEF
)(1
1)(
k ndash the Boltzman constant
T ndash the absolute temperature
- Fermi-Dirac
distribution function
8
Fermi level
kTEE FeEF
)(1
1)(
- Fermi-Dirac
distribution function
Fermi energy (EF) ndash is that energy value for which the probability of the state
being occupied is frac12
At T = 0 all energy states below EF are completely filled and above EF are
completely empty
Concentration of the electrons in the conduction band
32
( )
2
22 FE E kTe
e
m kTn e
h
Concentration increases when EF moves closer to conduction band
9
Intrinsic semiconductor
FERMI DISTRIBUTION F(E)
VERSUS (E ndash EF ) FOR
VARIOUS TEMPERATURES
The Fermi distribution function can be approximated by simpler expressions
kTEEforeEF F
kTEE F 3)(
kTEEforeEF F
kTEE F 31)(
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
10
Intrinsic semiconductor
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
(a) band
diagram
(b) density
of state (c) fermi
distribution
function
(d) Carrier
concentration
11
Doping bull The energy band
structure may be
modified by introducing
impurity atoms to the
crystal lattice (doping)
bull Eg silicon group IV
from the periodic table
4 outer electrons
bull Donor impurity atom
from the V group (eg
nitrogen phosphorus)
with 5 outer electrons ndash
the one free electron can
be easily lost to the
conduction band
bull Acceptor impurity
atom from the III group
(eg boron) ndash three outer
electrons contributes a
hole to the valence band We can modify the Fermi level by doping
12
p-n junction E
nerg
y
Ec
EV
Ec
EV
Ec
EV
EF EF
EF
p n
eV0
EF
p n
+
+
+
+
-
-
-
-
Energ
y
13
Semiconductors Part of the Periodic Table Related to Semiconductors
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
14
Semiconductors Typical compounds
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
15
Electroluminescence (LED)
16
p-n junction laser (homojunction)
Taken from [4] JT Verdeyen Laser Electronics Prentice Hall Englewood Cliffs 1995
Edge-emitting laser
17
Typical semiconductor laser
The ideal output power
against current
characteristic
Taken from [11] JM Senior Optical Fiber Communications Prentice Hall New York 1992
18
Threshold gaincurrent
Lets introduce threshold gain coefficient thg
depending on current density
threshold
thth Jg
where β is a constant appropriate to specific devices
Fractional loss Fl of the Fabry ndashPerot cavity is
LRRloss
2exp21
where
- single loss coefficient per unit round trip
Fractional gain of the Fabry ndashPerot cavity is
Lggain
2exp
where g
- single gain coefficient per unit round trip
19
Threshold gaincurrent The threshold case requires
12exp2exp 21 LRRLg
12exp21 LgRR
Hence
21
1ln
2
1
RRLg th
the gain threshold
So we can write
thth Jg
by transformation we can find the threshold value for current density
21
1ln
2
11
RRLJ th
20
Threshold gaincurrent Example
A GaAs injection laser has an optical cavity of length L = 250 μm and widh
w = 100 μm At normal operating temperature the gain factor
β = 21 10-3 [Acm-3] and the loss coefficient
= 10 refractive index n = 36
Assuming R1 = 1 and reflection of mirror 2 3201
12
2
n
nR
The threshold current may be obtain from the equation from the previous slide
2
3
21
106521
ln2
11
cm
A
RRLJ th
The threshold current
mAcavityopticaltheofareaJI thth 663
Taken from [11] JM Senior Optical Fiber Communications Prentice Hall New York 1992
21
Efficiency
Below the threshold laser acts like a LED
Above the threshold stimulated emission
dominates the spontaneous emission
causing laser emission
Formal definition of the efficiency η
For a laser with drive current I and a threshold
current Ithr the output power of the laser at
wavelength λ is
( )thr
hcP I I
e
22
bull More efficient diode lasers are based on heterojunctions
bull Heterojunction is formed between two different semiconductors with different bangap energies
bull Typical materials eg GaAs and AlGaAs
bull One semiconductor is sandwiched between two cladding layers of another semiconductor
Heterojunction lasers
23
Heterojunction laser
AlGaAs (n)
GaAs
Substrate n (GaAs)
AlGaAs (p) 1 μm
1 μm
015 μm
24
LED vs Laser diode
Power vs Current Spectral width
25
Materials amp wavelengths
Taken from Optics and Photonics an introduction 2nd edition Wiley
26
bull Fabry-Perot
bull Distributed Feedback (DFB)
bull Distributed Bragg Reflector (DBR)
bull Grating-stabilized laser
bull External cavity laser (ECL)
Cavities
27
Modes
Taken from [9] F Tragger Ed Springer Handbook of Lasers and Optics Springer New York 2007
28
bull Incorporates the grating within the laser diode structure itself
bull The Bragg grating selects only one mode
bull single-frequency operation over broad temperature and current ranges
bull Tuning 2-4 nm
bull Linewidth 1 ndash 10 MHz
Distributed feedback laser
29
bull The reflector is outsite the active section
bull Broad tuning range possible (up to 40 nm)
bull Mode hopping possible
Distributed Bragg Reflector
30
bull The grating stabilizes the wavelength of the laser (provides a small feedback)
bull Grating is outside the laser (it is not a laser mirror)
bull Might be placed on a fiber
Grating-stabilized lasers
31
External cavity lasers
bull A grating inside allows
wavelength tuning in a
broad range
bull The linewidths are very
narrow
bull bdquoBulkrdquo construction long
resonator
32
bull VCSEL
Surface emitting laser
bull Limited output power
bull Very small resonator
length (few micrometers)
bull Easy achievable single-
frequency operation
bull High modulation
frequency (useful in
telecom)
bull Most common emission
750 ndash 980 nm
33
bull VECSEL (Vertical External-cavity Surface-emitting Laser)
External cavity
34
VECSELs VECSELs enable optical pumping
35
bull TO can
Housings
36
bull C-mount
Housings
37
bull 14-pin Butterfly
Housings
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
6
Direct indirect bandgap In order to achieve electroluminescence it is necessary to select an appropriate
semiconductors material The most useful material for this purpose are so-called
DIRECT BANDGAP SEMICONDUCTORS
Direct bandgap semiconductors Indirect bandgap semiconductors
electron photon
or momentum p = 2πhk
valence band
wave vector k
conduction band
conduction band
k p = 2πhk
7
Intrinsic semiconductor An intrinsic semiconductor is one that contains relatively small amounts of
impurities At finite temperatures determines the excitation of electrons from the
valence band to the conduction band and levels an equal number of holes in the
valence band
The electron density n(E) (number of electrons per unit volume) in an
semiconductor is given by
toptop EE
dEEFENdEEnn )()()(
where N(E) - density of allowed energy states per unit volume
Etop - the top of the conduction band Etop
kTEE FeEF
)(1
1)(
k ndash the Boltzman constant
T ndash the absolute temperature
- Fermi-Dirac
distribution function
8
Fermi level
kTEE FeEF
)(1
1)(
- Fermi-Dirac
distribution function
Fermi energy (EF) ndash is that energy value for which the probability of the state
being occupied is frac12
At T = 0 all energy states below EF are completely filled and above EF are
completely empty
Concentration of the electrons in the conduction band
32
( )
2
22 FE E kTe
e
m kTn e
h
Concentration increases when EF moves closer to conduction band
9
Intrinsic semiconductor
FERMI DISTRIBUTION F(E)
VERSUS (E ndash EF ) FOR
VARIOUS TEMPERATURES
The Fermi distribution function can be approximated by simpler expressions
kTEEforeEF F
kTEE F 3)(
kTEEforeEF F
kTEE F 31)(
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
10
Intrinsic semiconductor
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
(a) band
diagram
(b) density
of state (c) fermi
distribution
function
(d) Carrier
concentration
11
Doping bull The energy band
structure may be
modified by introducing
impurity atoms to the
crystal lattice (doping)
bull Eg silicon group IV
from the periodic table
4 outer electrons
bull Donor impurity atom
from the V group (eg
nitrogen phosphorus)
with 5 outer electrons ndash
the one free electron can
be easily lost to the
conduction band
bull Acceptor impurity
atom from the III group
(eg boron) ndash three outer
electrons contributes a
hole to the valence band We can modify the Fermi level by doping
12
p-n junction E
nerg
y
Ec
EV
Ec
EV
Ec
EV
EF EF
EF
p n
eV0
EF
p n
+
+
+
+
-
-
-
-
Energ
y
13
Semiconductors Part of the Periodic Table Related to Semiconductors
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
14
Semiconductors Typical compounds
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
15
Electroluminescence (LED)
16
p-n junction laser (homojunction)
Taken from [4] JT Verdeyen Laser Electronics Prentice Hall Englewood Cliffs 1995
Edge-emitting laser
17
Typical semiconductor laser
The ideal output power
against current
characteristic
Taken from [11] JM Senior Optical Fiber Communications Prentice Hall New York 1992
18
Threshold gaincurrent
Lets introduce threshold gain coefficient thg
depending on current density
threshold
thth Jg
where β is a constant appropriate to specific devices
Fractional loss Fl of the Fabry ndashPerot cavity is
LRRloss
2exp21
where
- single loss coefficient per unit round trip
Fractional gain of the Fabry ndashPerot cavity is
Lggain
2exp
where g
- single gain coefficient per unit round trip
19
Threshold gaincurrent The threshold case requires
12exp2exp 21 LRRLg
12exp21 LgRR
Hence
21
1ln
2
1
RRLg th
the gain threshold
So we can write
thth Jg
by transformation we can find the threshold value for current density
21
1ln
2
11
RRLJ th
20
Threshold gaincurrent Example
A GaAs injection laser has an optical cavity of length L = 250 μm and widh
w = 100 μm At normal operating temperature the gain factor
β = 21 10-3 [Acm-3] and the loss coefficient
= 10 refractive index n = 36
Assuming R1 = 1 and reflection of mirror 2 3201
12
2
n
nR
The threshold current may be obtain from the equation from the previous slide
2
3
21
106521
ln2
11
cm
A
RRLJ th
The threshold current
mAcavityopticaltheofareaJI thth 663
Taken from [11] JM Senior Optical Fiber Communications Prentice Hall New York 1992
21
Efficiency
Below the threshold laser acts like a LED
Above the threshold stimulated emission
dominates the spontaneous emission
causing laser emission
Formal definition of the efficiency η
For a laser with drive current I and a threshold
current Ithr the output power of the laser at
wavelength λ is
( )thr
hcP I I
e
22
bull More efficient diode lasers are based on heterojunctions
bull Heterojunction is formed between two different semiconductors with different bangap energies
bull Typical materials eg GaAs and AlGaAs
bull One semiconductor is sandwiched between two cladding layers of another semiconductor
Heterojunction lasers
23
Heterojunction laser
AlGaAs (n)
GaAs
Substrate n (GaAs)
AlGaAs (p) 1 μm
1 μm
015 μm
24
LED vs Laser diode
Power vs Current Spectral width
25
Materials amp wavelengths
Taken from Optics and Photonics an introduction 2nd edition Wiley
26
bull Fabry-Perot
bull Distributed Feedback (DFB)
bull Distributed Bragg Reflector (DBR)
bull Grating-stabilized laser
bull External cavity laser (ECL)
Cavities
27
Modes
Taken from [9] F Tragger Ed Springer Handbook of Lasers and Optics Springer New York 2007
28
bull Incorporates the grating within the laser diode structure itself
bull The Bragg grating selects only one mode
bull single-frequency operation over broad temperature and current ranges
bull Tuning 2-4 nm
bull Linewidth 1 ndash 10 MHz
Distributed feedback laser
29
bull The reflector is outsite the active section
bull Broad tuning range possible (up to 40 nm)
bull Mode hopping possible
Distributed Bragg Reflector
30
bull The grating stabilizes the wavelength of the laser (provides a small feedback)
bull Grating is outside the laser (it is not a laser mirror)
bull Might be placed on a fiber
Grating-stabilized lasers
31
External cavity lasers
bull A grating inside allows
wavelength tuning in a
broad range
bull The linewidths are very
narrow
bull bdquoBulkrdquo construction long
resonator
32
bull VCSEL
Surface emitting laser
bull Limited output power
bull Very small resonator
length (few micrometers)
bull Easy achievable single-
frequency operation
bull High modulation
frequency (useful in
telecom)
bull Most common emission
750 ndash 980 nm
33
bull VECSEL (Vertical External-cavity Surface-emitting Laser)
External cavity
34
VECSELs VECSELs enable optical pumping
35
bull TO can
Housings
36
bull C-mount
Housings
37
bull 14-pin Butterfly
Housings
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
7
Intrinsic semiconductor An intrinsic semiconductor is one that contains relatively small amounts of
impurities At finite temperatures determines the excitation of electrons from the
valence band to the conduction band and levels an equal number of holes in the
valence band
The electron density n(E) (number of electrons per unit volume) in an
semiconductor is given by
toptop EE
dEEFENdEEnn )()()(
where N(E) - density of allowed energy states per unit volume
Etop - the top of the conduction band Etop
kTEE FeEF
)(1
1)(
k ndash the Boltzman constant
T ndash the absolute temperature
- Fermi-Dirac
distribution function
8
Fermi level
kTEE FeEF
)(1
1)(
- Fermi-Dirac
distribution function
Fermi energy (EF) ndash is that energy value for which the probability of the state
being occupied is frac12
At T = 0 all energy states below EF are completely filled and above EF are
completely empty
Concentration of the electrons in the conduction band
32
( )
2
22 FE E kTe
e
m kTn e
h
Concentration increases when EF moves closer to conduction band
9
Intrinsic semiconductor
FERMI DISTRIBUTION F(E)
VERSUS (E ndash EF ) FOR
VARIOUS TEMPERATURES
The Fermi distribution function can be approximated by simpler expressions
kTEEforeEF F
kTEE F 3)(
kTEEforeEF F
kTEE F 31)(
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
10
Intrinsic semiconductor
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
(a) band
diagram
(b) density
of state (c) fermi
distribution
function
(d) Carrier
concentration
11
Doping bull The energy band
structure may be
modified by introducing
impurity atoms to the
crystal lattice (doping)
bull Eg silicon group IV
from the periodic table
4 outer electrons
bull Donor impurity atom
from the V group (eg
nitrogen phosphorus)
with 5 outer electrons ndash
the one free electron can
be easily lost to the
conduction band
bull Acceptor impurity
atom from the III group
(eg boron) ndash three outer
electrons contributes a
hole to the valence band We can modify the Fermi level by doping
12
p-n junction E
nerg
y
Ec
EV
Ec
EV
Ec
EV
EF EF
EF
p n
eV0
EF
p n
+
+
+
+
-
-
-
-
Energ
y
13
Semiconductors Part of the Periodic Table Related to Semiconductors
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
14
Semiconductors Typical compounds
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
15
Electroluminescence (LED)
16
p-n junction laser (homojunction)
Taken from [4] JT Verdeyen Laser Electronics Prentice Hall Englewood Cliffs 1995
Edge-emitting laser
17
Typical semiconductor laser
The ideal output power
against current
characteristic
Taken from [11] JM Senior Optical Fiber Communications Prentice Hall New York 1992
18
Threshold gaincurrent
Lets introduce threshold gain coefficient thg
depending on current density
threshold
thth Jg
where β is a constant appropriate to specific devices
Fractional loss Fl of the Fabry ndashPerot cavity is
LRRloss
2exp21
where
- single loss coefficient per unit round trip
Fractional gain of the Fabry ndashPerot cavity is
Lggain
2exp
where g
- single gain coefficient per unit round trip
19
Threshold gaincurrent The threshold case requires
12exp2exp 21 LRRLg
12exp21 LgRR
Hence
21
1ln
2
1
RRLg th
the gain threshold
So we can write
thth Jg
by transformation we can find the threshold value for current density
21
1ln
2
11
RRLJ th
20
Threshold gaincurrent Example
A GaAs injection laser has an optical cavity of length L = 250 μm and widh
w = 100 μm At normal operating temperature the gain factor
β = 21 10-3 [Acm-3] and the loss coefficient
= 10 refractive index n = 36
Assuming R1 = 1 and reflection of mirror 2 3201
12
2
n
nR
The threshold current may be obtain from the equation from the previous slide
2
3
21
106521
ln2
11
cm
A
RRLJ th
The threshold current
mAcavityopticaltheofareaJI thth 663
Taken from [11] JM Senior Optical Fiber Communications Prentice Hall New York 1992
21
Efficiency
Below the threshold laser acts like a LED
Above the threshold stimulated emission
dominates the spontaneous emission
causing laser emission
Formal definition of the efficiency η
For a laser with drive current I and a threshold
current Ithr the output power of the laser at
wavelength λ is
( )thr
hcP I I
e
22
bull More efficient diode lasers are based on heterojunctions
bull Heterojunction is formed between two different semiconductors with different bangap energies
bull Typical materials eg GaAs and AlGaAs
bull One semiconductor is sandwiched between two cladding layers of another semiconductor
Heterojunction lasers
23
Heterojunction laser
AlGaAs (n)
GaAs
Substrate n (GaAs)
AlGaAs (p) 1 μm
1 μm
015 μm
24
LED vs Laser diode
Power vs Current Spectral width
25
Materials amp wavelengths
Taken from Optics and Photonics an introduction 2nd edition Wiley
26
bull Fabry-Perot
bull Distributed Feedback (DFB)
bull Distributed Bragg Reflector (DBR)
bull Grating-stabilized laser
bull External cavity laser (ECL)
Cavities
27
Modes
Taken from [9] F Tragger Ed Springer Handbook of Lasers and Optics Springer New York 2007
28
bull Incorporates the grating within the laser diode structure itself
bull The Bragg grating selects only one mode
bull single-frequency operation over broad temperature and current ranges
bull Tuning 2-4 nm
bull Linewidth 1 ndash 10 MHz
Distributed feedback laser
29
bull The reflector is outsite the active section
bull Broad tuning range possible (up to 40 nm)
bull Mode hopping possible
Distributed Bragg Reflector
30
bull The grating stabilizes the wavelength of the laser (provides a small feedback)
bull Grating is outside the laser (it is not a laser mirror)
bull Might be placed on a fiber
Grating-stabilized lasers
31
External cavity lasers
bull A grating inside allows
wavelength tuning in a
broad range
bull The linewidths are very
narrow
bull bdquoBulkrdquo construction long
resonator
32
bull VCSEL
Surface emitting laser
bull Limited output power
bull Very small resonator
length (few micrometers)
bull Easy achievable single-
frequency operation
bull High modulation
frequency (useful in
telecom)
bull Most common emission
750 ndash 980 nm
33
bull VECSEL (Vertical External-cavity Surface-emitting Laser)
External cavity
34
VECSELs VECSELs enable optical pumping
35
bull TO can
Housings
36
bull C-mount
Housings
37
bull 14-pin Butterfly
Housings
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
8
Fermi level
kTEE FeEF
)(1
1)(
- Fermi-Dirac
distribution function
Fermi energy (EF) ndash is that energy value for which the probability of the state
being occupied is frac12
At T = 0 all energy states below EF are completely filled and above EF are
completely empty
Concentration of the electrons in the conduction band
32
( )
2
22 FE E kTe
e
m kTn e
h
Concentration increases when EF moves closer to conduction band
9
Intrinsic semiconductor
FERMI DISTRIBUTION F(E)
VERSUS (E ndash EF ) FOR
VARIOUS TEMPERATURES
The Fermi distribution function can be approximated by simpler expressions
kTEEforeEF F
kTEE F 3)(
kTEEforeEF F
kTEE F 31)(
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
10
Intrinsic semiconductor
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
(a) band
diagram
(b) density
of state (c) fermi
distribution
function
(d) Carrier
concentration
11
Doping bull The energy band
structure may be
modified by introducing
impurity atoms to the
crystal lattice (doping)
bull Eg silicon group IV
from the periodic table
4 outer electrons
bull Donor impurity atom
from the V group (eg
nitrogen phosphorus)
with 5 outer electrons ndash
the one free electron can
be easily lost to the
conduction band
bull Acceptor impurity
atom from the III group
(eg boron) ndash three outer
electrons contributes a
hole to the valence band We can modify the Fermi level by doping
12
p-n junction E
nerg
y
Ec
EV
Ec
EV
Ec
EV
EF EF
EF
p n
eV0
EF
p n
+
+
+
+
-
-
-
-
Energ
y
13
Semiconductors Part of the Periodic Table Related to Semiconductors
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
14
Semiconductors Typical compounds
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
15
Electroluminescence (LED)
16
p-n junction laser (homojunction)
Taken from [4] JT Verdeyen Laser Electronics Prentice Hall Englewood Cliffs 1995
Edge-emitting laser
17
Typical semiconductor laser
The ideal output power
against current
characteristic
Taken from [11] JM Senior Optical Fiber Communications Prentice Hall New York 1992
18
Threshold gaincurrent
Lets introduce threshold gain coefficient thg
depending on current density
threshold
thth Jg
where β is a constant appropriate to specific devices
Fractional loss Fl of the Fabry ndashPerot cavity is
LRRloss
2exp21
where
- single loss coefficient per unit round trip
Fractional gain of the Fabry ndashPerot cavity is
Lggain
2exp
where g
- single gain coefficient per unit round trip
19
Threshold gaincurrent The threshold case requires
12exp2exp 21 LRRLg
12exp21 LgRR
Hence
21
1ln
2
1
RRLg th
the gain threshold
So we can write
thth Jg
by transformation we can find the threshold value for current density
21
1ln
2
11
RRLJ th
20
Threshold gaincurrent Example
A GaAs injection laser has an optical cavity of length L = 250 μm and widh
w = 100 μm At normal operating temperature the gain factor
β = 21 10-3 [Acm-3] and the loss coefficient
= 10 refractive index n = 36
Assuming R1 = 1 and reflection of mirror 2 3201
12
2
n
nR
The threshold current may be obtain from the equation from the previous slide
2
3
21
106521
ln2
11
cm
A
RRLJ th
The threshold current
mAcavityopticaltheofareaJI thth 663
Taken from [11] JM Senior Optical Fiber Communications Prentice Hall New York 1992
21
Efficiency
Below the threshold laser acts like a LED
Above the threshold stimulated emission
dominates the spontaneous emission
causing laser emission
Formal definition of the efficiency η
For a laser with drive current I and a threshold
current Ithr the output power of the laser at
wavelength λ is
( )thr
hcP I I
e
22
bull More efficient diode lasers are based on heterojunctions
bull Heterojunction is formed between two different semiconductors with different bangap energies
bull Typical materials eg GaAs and AlGaAs
bull One semiconductor is sandwiched between two cladding layers of another semiconductor
Heterojunction lasers
23
Heterojunction laser
AlGaAs (n)
GaAs
Substrate n (GaAs)
AlGaAs (p) 1 μm
1 μm
015 μm
24
LED vs Laser diode
Power vs Current Spectral width
25
Materials amp wavelengths
Taken from Optics and Photonics an introduction 2nd edition Wiley
26
bull Fabry-Perot
bull Distributed Feedback (DFB)
bull Distributed Bragg Reflector (DBR)
bull Grating-stabilized laser
bull External cavity laser (ECL)
Cavities
27
Modes
Taken from [9] F Tragger Ed Springer Handbook of Lasers and Optics Springer New York 2007
28
bull Incorporates the grating within the laser diode structure itself
bull The Bragg grating selects only one mode
bull single-frequency operation over broad temperature and current ranges
bull Tuning 2-4 nm
bull Linewidth 1 ndash 10 MHz
Distributed feedback laser
29
bull The reflector is outsite the active section
bull Broad tuning range possible (up to 40 nm)
bull Mode hopping possible
Distributed Bragg Reflector
30
bull The grating stabilizes the wavelength of the laser (provides a small feedback)
bull Grating is outside the laser (it is not a laser mirror)
bull Might be placed on a fiber
Grating-stabilized lasers
31
External cavity lasers
bull A grating inside allows
wavelength tuning in a
broad range
bull The linewidths are very
narrow
bull bdquoBulkrdquo construction long
resonator
32
bull VCSEL
Surface emitting laser
bull Limited output power
bull Very small resonator
length (few micrometers)
bull Easy achievable single-
frequency operation
bull High modulation
frequency (useful in
telecom)
bull Most common emission
750 ndash 980 nm
33
bull VECSEL (Vertical External-cavity Surface-emitting Laser)
External cavity
34
VECSELs VECSELs enable optical pumping
35
bull TO can
Housings
36
bull C-mount
Housings
37
bull 14-pin Butterfly
Housings
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
9
Intrinsic semiconductor
FERMI DISTRIBUTION F(E)
VERSUS (E ndash EF ) FOR
VARIOUS TEMPERATURES
The Fermi distribution function can be approximated by simpler expressions
kTEEforeEF F
kTEE F 3)(
kTEEforeEF F
kTEE F 31)(
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
10
Intrinsic semiconductor
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
(a) band
diagram
(b) density
of state (c) fermi
distribution
function
(d) Carrier
concentration
11
Doping bull The energy band
structure may be
modified by introducing
impurity atoms to the
crystal lattice (doping)
bull Eg silicon group IV
from the periodic table
4 outer electrons
bull Donor impurity atom
from the V group (eg
nitrogen phosphorus)
with 5 outer electrons ndash
the one free electron can
be easily lost to the
conduction band
bull Acceptor impurity
atom from the III group
(eg boron) ndash three outer
electrons contributes a
hole to the valence band We can modify the Fermi level by doping
12
p-n junction E
nerg
y
Ec
EV
Ec
EV
Ec
EV
EF EF
EF
p n
eV0
EF
p n
+
+
+
+
-
-
-
-
Energ
y
13
Semiconductors Part of the Periodic Table Related to Semiconductors
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
14
Semiconductors Typical compounds
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
15
Electroluminescence (LED)
16
p-n junction laser (homojunction)
Taken from [4] JT Verdeyen Laser Electronics Prentice Hall Englewood Cliffs 1995
Edge-emitting laser
17
Typical semiconductor laser
The ideal output power
against current
characteristic
Taken from [11] JM Senior Optical Fiber Communications Prentice Hall New York 1992
18
Threshold gaincurrent
Lets introduce threshold gain coefficient thg
depending on current density
threshold
thth Jg
where β is a constant appropriate to specific devices
Fractional loss Fl of the Fabry ndashPerot cavity is
LRRloss
2exp21
where
- single loss coefficient per unit round trip
Fractional gain of the Fabry ndashPerot cavity is
Lggain
2exp
where g
- single gain coefficient per unit round trip
19
Threshold gaincurrent The threshold case requires
12exp2exp 21 LRRLg
12exp21 LgRR
Hence
21
1ln
2
1
RRLg th
the gain threshold
So we can write
thth Jg
by transformation we can find the threshold value for current density
21
1ln
2
11
RRLJ th
20
Threshold gaincurrent Example
A GaAs injection laser has an optical cavity of length L = 250 μm and widh
w = 100 μm At normal operating temperature the gain factor
β = 21 10-3 [Acm-3] and the loss coefficient
= 10 refractive index n = 36
Assuming R1 = 1 and reflection of mirror 2 3201
12
2
n
nR
The threshold current may be obtain from the equation from the previous slide
2
3
21
106521
ln2
11
cm
A
RRLJ th
The threshold current
mAcavityopticaltheofareaJI thth 663
Taken from [11] JM Senior Optical Fiber Communications Prentice Hall New York 1992
21
Efficiency
Below the threshold laser acts like a LED
Above the threshold stimulated emission
dominates the spontaneous emission
causing laser emission
Formal definition of the efficiency η
For a laser with drive current I and a threshold
current Ithr the output power of the laser at
wavelength λ is
( )thr
hcP I I
e
22
bull More efficient diode lasers are based on heterojunctions
bull Heterojunction is formed between two different semiconductors with different bangap energies
bull Typical materials eg GaAs and AlGaAs
bull One semiconductor is sandwiched between two cladding layers of another semiconductor
Heterojunction lasers
23
Heterojunction laser
AlGaAs (n)
GaAs
Substrate n (GaAs)
AlGaAs (p) 1 μm
1 μm
015 μm
24
LED vs Laser diode
Power vs Current Spectral width
25
Materials amp wavelengths
Taken from Optics and Photonics an introduction 2nd edition Wiley
26
bull Fabry-Perot
bull Distributed Feedback (DFB)
bull Distributed Bragg Reflector (DBR)
bull Grating-stabilized laser
bull External cavity laser (ECL)
Cavities
27
Modes
Taken from [9] F Tragger Ed Springer Handbook of Lasers and Optics Springer New York 2007
28
bull Incorporates the grating within the laser diode structure itself
bull The Bragg grating selects only one mode
bull single-frequency operation over broad temperature and current ranges
bull Tuning 2-4 nm
bull Linewidth 1 ndash 10 MHz
Distributed feedback laser
29
bull The reflector is outsite the active section
bull Broad tuning range possible (up to 40 nm)
bull Mode hopping possible
Distributed Bragg Reflector
30
bull The grating stabilizes the wavelength of the laser (provides a small feedback)
bull Grating is outside the laser (it is not a laser mirror)
bull Might be placed on a fiber
Grating-stabilized lasers
31
External cavity lasers
bull A grating inside allows
wavelength tuning in a
broad range
bull The linewidths are very
narrow
bull bdquoBulkrdquo construction long
resonator
32
bull VCSEL
Surface emitting laser
bull Limited output power
bull Very small resonator
length (few micrometers)
bull Easy achievable single-
frequency operation
bull High modulation
frequency (useful in
telecom)
bull Most common emission
750 ndash 980 nm
33
bull VECSEL (Vertical External-cavity Surface-emitting Laser)
External cavity
34
VECSELs VECSELs enable optical pumping
35
bull TO can
Housings
36
bull C-mount
Housings
37
bull 14-pin Butterfly
Housings
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
10
Intrinsic semiconductor
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
(a) band
diagram
(b) density
of state (c) fermi
distribution
function
(d) Carrier
concentration
11
Doping bull The energy band
structure may be
modified by introducing
impurity atoms to the
crystal lattice (doping)
bull Eg silicon group IV
from the periodic table
4 outer electrons
bull Donor impurity atom
from the V group (eg
nitrogen phosphorus)
with 5 outer electrons ndash
the one free electron can
be easily lost to the
conduction band
bull Acceptor impurity
atom from the III group
(eg boron) ndash three outer
electrons contributes a
hole to the valence band We can modify the Fermi level by doping
12
p-n junction E
nerg
y
Ec
EV
Ec
EV
Ec
EV
EF EF
EF
p n
eV0
EF
p n
+
+
+
+
-
-
-
-
Energ
y
13
Semiconductors Part of the Periodic Table Related to Semiconductors
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
14
Semiconductors Typical compounds
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
15
Electroluminescence (LED)
16
p-n junction laser (homojunction)
Taken from [4] JT Verdeyen Laser Electronics Prentice Hall Englewood Cliffs 1995
Edge-emitting laser
17
Typical semiconductor laser
The ideal output power
against current
characteristic
Taken from [11] JM Senior Optical Fiber Communications Prentice Hall New York 1992
18
Threshold gaincurrent
Lets introduce threshold gain coefficient thg
depending on current density
threshold
thth Jg
where β is a constant appropriate to specific devices
Fractional loss Fl of the Fabry ndashPerot cavity is
LRRloss
2exp21
where
- single loss coefficient per unit round trip
Fractional gain of the Fabry ndashPerot cavity is
Lggain
2exp
where g
- single gain coefficient per unit round trip
19
Threshold gaincurrent The threshold case requires
12exp2exp 21 LRRLg
12exp21 LgRR
Hence
21
1ln
2
1
RRLg th
the gain threshold
So we can write
thth Jg
by transformation we can find the threshold value for current density
21
1ln
2
11
RRLJ th
20
Threshold gaincurrent Example
A GaAs injection laser has an optical cavity of length L = 250 μm and widh
w = 100 μm At normal operating temperature the gain factor
β = 21 10-3 [Acm-3] and the loss coefficient
= 10 refractive index n = 36
Assuming R1 = 1 and reflection of mirror 2 3201
12
2
n
nR
The threshold current may be obtain from the equation from the previous slide
2
3
21
106521
ln2
11
cm
A
RRLJ th
The threshold current
mAcavityopticaltheofareaJI thth 663
Taken from [11] JM Senior Optical Fiber Communications Prentice Hall New York 1992
21
Efficiency
Below the threshold laser acts like a LED
Above the threshold stimulated emission
dominates the spontaneous emission
causing laser emission
Formal definition of the efficiency η
For a laser with drive current I and a threshold
current Ithr the output power of the laser at
wavelength λ is
( )thr
hcP I I
e
22
bull More efficient diode lasers are based on heterojunctions
bull Heterojunction is formed between two different semiconductors with different bangap energies
bull Typical materials eg GaAs and AlGaAs
bull One semiconductor is sandwiched between two cladding layers of another semiconductor
Heterojunction lasers
23
Heterojunction laser
AlGaAs (n)
GaAs
Substrate n (GaAs)
AlGaAs (p) 1 μm
1 μm
015 μm
24
LED vs Laser diode
Power vs Current Spectral width
25
Materials amp wavelengths
Taken from Optics and Photonics an introduction 2nd edition Wiley
26
bull Fabry-Perot
bull Distributed Feedback (DFB)
bull Distributed Bragg Reflector (DBR)
bull Grating-stabilized laser
bull External cavity laser (ECL)
Cavities
27
Modes
Taken from [9] F Tragger Ed Springer Handbook of Lasers and Optics Springer New York 2007
28
bull Incorporates the grating within the laser diode structure itself
bull The Bragg grating selects only one mode
bull single-frequency operation over broad temperature and current ranges
bull Tuning 2-4 nm
bull Linewidth 1 ndash 10 MHz
Distributed feedback laser
29
bull The reflector is outsite the active section
bull Broad tuning range possible (up to 40 nm)
bull Mode hopping possible
Distributed Bragg Reflector
30
bull The grating stabilizes the wavelength of the laser (provides a small feedback)
bull Grating is outside the laser (it is not a laser mirror)
bull Might be placed on a fiber
Grating-stabilized lasers
31
External cavity lasers
bull A grating inside allows
wavelength tuning in a
broad range
bull The linewidths are very
narrow
bull bdquoBulkrdquo construction long
resonator
32
bull VCSEL
Surface emitting laser
bull Limited output power
bull Very small resonator
length (few micrometers)
bull Easy achievable single-
frequency operation
bull High modulation
frequency (useful in
telecom)
bull Most common emission
750 ndash 980 nm
33
bull VECSEL (Vertical External-cavity Surface-emitting Laser)
External cavity
34
VECSELs VECSELs enable optical pumping
35
bull TO can
Housings
36
bull C-mount
Housings
37
bull 14-pin Butterfly
Housings
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
11
Doping bull The energy band
structure may be
modified by introducing
impurity atoms to the
crystal lattice (doping)
bull Eg silicon group IV
from the periodic table
4 outer electrons
bull Donor impurity atom
from the V group (eg
nitrogen phosphorus)
with 5 outer electrons ndash
the one free electron can
be easily lost to the
conduction band
bull Acceptor impurity
atom from the III group
(eg boron) ndash three outer
electrons contributes a
hole to the valence band We can modify the Fermi level by doping
12
p-n junction E
nerg
y
Ec
EV
Ec
EV
Ec
EV
EF EF
EF
p n
eV0
EF
p n
+
+
+
+
-
-
-
-
Energ
y
13
Semiconductors Part of the Periodic Table Related to Semiconductors
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
14
Semiconductors Typical compounds
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
15
Electroluminescence (LED)
16
p-n junction laser (homojunction)
Taken from [4] JT Verdeyen Laser Electronics Prentice Hall Englewood Cliffs 1995
Edge-emitting laser
17
Typical semiconductor laser
The ideal output power
against current
characteristic
Taken from [11] JM Senior Optical Fiber Communications Prentice Hall New York 1992
18
Threshold gaincurrent
Lets introduce threshold gain coefficient thg
depending on current density
threshold
thth Jg
where β is a constant appropriate to specific devices
Fractional loss Fl of the Fabry ndashPerot cavity is
LRRloss
2exp21
where
- single loss coefficient per unit round trip
Fractional gain of the Fabry ndashPerot cavity is
Lggain
2exp
where g
- single gain coefficient per unit round trip
19
Threshold gaincurrent The threshold case requires
12exp2exp 21 LRRLg
12exp21 LgRR
Hence
21
1ln
2
1
RRLg th
the gain threshold
So we can write
thth Jg
by transformation we can find the threshold value for current density
21
1ln
2
11
RRLJ th
20
Threshold gaincurrent Example
A GaAs injection laser has an optical cavity of length L = 250 μm and widh
w = 100 μm At normal operating temperature the gain factor
β = 21 10-3 [Acm-3] and the loss coefficient
= 10 refractive index n = 36
Assuming R1 = 1 and reflection of mirror 2 3201
12
2
n
nR
The threshold current may be obtain from the equation from the previous slide
2
3
21
106521
ln2
11
cm
A
RRLJ th
The threshold current
mAcavityopticaltheofareaJI thth 663
Taken from [11] JM Senior Optical Fiber Communications Prentice Hall New York 1992
21
Efficiency
Below the threshold laser acts like a LED
Above the threshold stimulated emission
dominates the spontaneous emission
causing laser emission
Formal definition of the efficiency η
For a laser with drive current I and a threshold
current Ithr the output power of the laser at
wavelength λ is
( )thr
hcP I I
e
22
bull More efficient diode lasers are based on heterojunctions
bull Heterojunction is formed between two different semiconductors with different bangap energies
bull Typical materials eg GaAs and AlGaAs
bull One semiconductor is sandwiched between two cladding layers of another semiconductor
Heterojunction lasers
23
Heterojunction laser
AlGaAs (n)
GaAs
Substrate n (GaAs)
AlGaAs (p) 1 μm
1 μm
015 μm
24
LED vs Laser diode
Power vs Current Spectral width
25
Materials amp wavelengths
Taken from Optics and Photonics an introduction 2nd edition Wiley
26
bull Fabry-Perot
bull Distributed Feedback (DFB)
bull Distributed Bragg Reflector (DBR)
bull Grating-stabilized laser
bull External cavity laser (ECL)
Cavities
27
Modes
Taken from [9] F Tragger Ed Springer Handbook of Lasers and Optics Springer New York 2007
28
bull Incorporates the grating within the laser diode structure itself
bull The Bragg grating selects only one mode
bull single-frequency operation over broad temperature and current ranges
bull Tuning 2-4 nm
bull Linewidth 1 ndash 10 MHz
Distributed feedback laser
29
bull The reflector is outsite the active section
bull Broad tuning range possible (up to 40 nm)
bull Mode hopping possible
Distributed Bragg Reflector
30
bull The grating stabilizes the wavelength of the laser (provides a small feedback)
bull Grating is outside the laser (it is not a laser mirror)
bull Might be placed on a fiber
Grating-stabilized lasers
31
External cavity lasers
bull A grating inside allows
wavelength tuning in a
broad range
bull The linewidths are very
narrow
bull bdquoBulkrdquo construction long
resonator
32
bull VCSEL
Surface emitting laser
bull Limited output power
bull Very small resonator
length (few micrometers)
bull Easy achievable single-
frequency operation
bull High modulation
frequency (useful in
telecom)
bull Most common emission
750 ndash 980 nm
33
bull VECSEL (Vertical External-cavity Surface-emitting Laser)
External cavity
34
VECSELs VECSELs enable optical pumping
35
bull TO can
Housings
36
bull C-mount
Housings
37
bull 14-pin Butterfly
Housings
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
12
p-n junction E
nerg
y
Ec
EV
Ec
EV
Ec
EV
EF EF
EF
p n
eV0
EF
p n
+
+
+
+
-
-
-
-
Energ
y
13
Semiconductors Part of the Periodic Table Related to Semiconductors
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
14
Semiconductors Typical compounds
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
15
Electroluminescence (LED)
16
p-n junction laser (homojunction)
Taken from [4] JT Verdeyen Laser Electronics Prentice Hall Englewood Cliffs 1995
Edge-emitting laser
17
Typical semiconductor laser
The ideal output power
against current
characteristic
Taken from [11] JM Senior Optical Fiber Communications Prentice Hall New York 1992
18
Threshold gaincurrent
Lets introduce threshold gain coefficient thg
depending on current density
threshold
thth Jg
where β is a constant appropriate to specific devices
Fractional loss Fl of the Fabry ndashPerot cavity is
LRRloss
2exp21
where
- single loss coefficient per unit round trip
Fractional gain of the Fabry ndashPerot cavity is
Lggain
2exp
where g
- single gain coefficient per unit round trip
19
Threshold gaincurrent The threshold case requires
12exp2exp 21 LRRLg
12exp21 LgRR
Hence
21
1ln
2
1
RRLg th
the gain threshold
So we can write
thth Jg
by transformation we can find the threshold value for current density
21
1ln
2
11
RRLJ th
20
Threshold gaincurrent Example
A GaAs injection laser has an optical cavity of length L = 250 μm and widh
w = 100 μm At normal operating temperature the gain factor
β = 21 10-3 [Acm-3] and the loss coefficient
= 10 refractive index n = 36
Assuming R1 = 1 and reflection of mirror 2 3201
12
2
n
nR
The threshold current may be obtain from the equation from the previous slide
2
3
21
106521
ln2
11
cm
A
RRLJ th
The threshold current
mAcavityopticaltheofareaJI thth 663
Taken from [11] JM Senior Optical Fiber Communications Prentice Hall New York 1992
21
Efficiency
Below the threshold laser acts like a LED
Above the threshold stimulated emission
dominates the spontaneous emission
causing laser emission
Formal definition of the efficiency η
For a laser with drive current I and a threshold
current Ithr the output power of the laser at
wavelength λ is
( )thr
hcP I I
e
22
bull More efficient diode lasers are based on heterojunctions
bull Heterojunction is formed between two different semiconductors with different bangap energies
bull Typical materials eg GaAs and AlGaAs
bull One semiconductor is sandwiched between two cladding layers of another semiconductor
Heterojunction lasers
23
Heterojunction laser
AlGaAs (n)
GaAs
Substrate n (GaAs)
AlGaAs (p) 1 μm
1 μm
015 μm
24
LED vs Laser diode
Power vs Current Spectral width
25
Materials amp wavelengths
Taken from Optics and Photonics an introduction 2nd edition Wiley
26
bull Fabry-Perot
bull Distributed Feedback (DFB)
bull Distributed Bragg Reflector (DBR)
bull Grating-stabilized laser
bull External cavity laser (ECL)
Cavities
27
Modes
Taken from [9] F Tragger Ed Springer Handbook of Lasers and Optics Springer New York 2007
28
bull Incorporates the grating within the laser diode structure itself
bull The Bragg grating selects only one mode
bull single-frequency operation over broad temperature and current ranges
bull Tuning 2-4 nm
bull Linewidth 1 ndash 10 MHz
Distributed feedback laser
29
bull The reflector is outsite the active section
bull Broad tuning range possible (up to 40 nm)
bull Mode hopping possible
Distributed Bragg Reflector
30
bull The grating stabilizes the wavelength of the laser (provides a small feedback)
bull Grating is outside the laser (it is not a laser mirror)
bull Might be placed on a fiber
Grating-stabilized lasers
31
External cavity lasers
bull A grating inside allows
wavelength tuning in a
broad range
bull The linewidths are very
narrow
bull bdquoBulkrdquo construction long
resonator
32
bull VCSEL
Surface emitting laser
bull Limited output power
bull Very small resonator
length (few micrometers)
bull Easy achievable single-
frequency operation
bull High modulation
frequency (useful in
telecom)
bull Most common emission
750 ndash 980 nm
33
bull VECSEL (Vertical External-cavity Surface-emitting Laser)
External cavity
34
VECSELs VECSELs enable optical pumping
35
bull TO can
Housings
36
bull C-mount
Housings
37
bull 14-pin Butterfly
Housings
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
13
Semiconductors Part of the Periodic Table Related to Semiconductors
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
14
Semiconductors Typical compounds
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
15
Electroluminescence (LED)
16
p-n junction laser (homojunction)
Taken from [4] JT Verdeyen Laser Electronics Prentice Hall Englewood Cliffs 1995
Edge-emitting laser
17
Typical semiconductor laser
The ideal output power
against current
characteristic
Taken from [11] JM Senior Optical Fiber Communications Prentice Hall New York 1992
18
Threshold gaincurrent
Lets introduce threshold gain coefficient thg
depending on current density
threshold
thth Jg
where β is a constant appropriate to specific devices
Fractional loss Fl of the Fabry ndashPerot cavity is
LRRloss
2exp21
where
- single loss coefficient per unit round trip
Fractional gain of the Fabry ndashPerot cavity is
Lggain
2exp
where g
- single gain coefficient per unit round trip
19
Threshold gaincurrent The threshold case requires
12exp2exp 21 LRRLg
12exp21 LgRR
Hence
21
1ln
2
1
RRLg th
the gain threshold
So we can write
thth Jg
by transformation we can find the threshold value for current density
21
1ln
2
11
RRLJ th
20
Threshold gaincurrent Example
A GaAs injection laser has an optical cavity of length L = 250 μm and widh
w = 100 μm At normal operating temperature the gain factor
β = 21 10-3 [Acm-3] and the loss coefficient
= 10 refractive index n = 36
Assuming R1 = 1 and reflection of mirror 2 3201
12
2
n
nR
The threshold current may be obtain from the equation from the previous slide
2
3
21
106521
ln2
11
cm
A
RRLJ th
The threshold current
mAcavityopticaltheofareaJI thth 663
Taken from [11] JM Senior Optical Fiber Communications Prentice Hall New York 1992
21
Efficiency
Below the threshold laser acts like a LED
Above the threshold stimulated emission
dominates the spontaneous emission
causing laser emission
Formal definition of the efficiency η
For a laser with drive current I and a threshold
current Ithr the output power of the laser at
wavelength λ is
( )thr
hcP I I
e
22
bull More efficient diode lasers are based on heterojunctions
bull Heterojunction is formed between two different semiconductors with different bangap energies
bull Typical materials eg GaAs and AlGaAs
bull One semiconductor is sandwiched between two cladding layers of another semiconductor
Heterojunction lasers
23
Heterojunction laser
AlGaAs (n)
GaAs
Substrate n (GaAs)
AlGaAs (p) 1 μm
1 μm
015 μm
24
LED vs Laser diode
Power vs Current Spectral width
25
Materials amp wavelengths
Taken from Optics and Photonics an introduction 2nd edition Wiley
26
bull Fabry-Perot
bull Distributed Feedback (DFB)
bull Distributed Bragg Reflector (DBR)
bull Grating-stabilized laser
bull External cavity laser (ECL)
Cavities
27
Modes
Taken from [9] F Tragger Ed Springer Handbook of Lasers and Optics Springer New York 2007
28
bull Incorporates the grating within the laser diode structure itself
bull The Bragg grating selects only one mode
bull single-frequency operation over broad temperature and current ranges
bull Tuning 2-4 nm
bull Linewidth 1 ndash 10 MHz
Distributed feedback laser
29
bull The reflector is outsite the active section
bull Broad tuning range possible (up to 40 nm)
bull Mode hopping possible
Distributed Bragg Reflector
30
bull The grating stabilizes the wavelength of the laser (provides a small feedback)
bull Grating is outside the laser (it is not a laser mirror)
bull Might be placed on a fiber
Grating-stabilized lasers
31
External cavity lasers
bull A grating inside allows
wavelength tuning in a
broad range
bull The linewidths are very
narrow
bull bdquoBulkrdquo construction long
resonator
32
bull VCSEL
Surface emitting laser
bull Limited output power
bull Very small resonator
length (few micrometers)
bull Easy achievable single-
frequency operation
bull High modulation
frequency (useful in
telecom)
bull Most common emission
750 ndash 980 nm
33
bull VECSEL (Vertical External-cavity Surface-emitting Laser)
External cavity
34
VECSELs VECSELs enable optical pumping
35
bull TO can
Housings
36
bull C-mount
Housings
37
bull 14-pin Butterfly
Housings
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
14
Semiconductors Typical compounds
Taken from [10] SM Sze Semiconductor Devices Physics and Technology John Wiley amp Sons New York1992
15
Electroluminescence (LED)
16
p-n junction laser (homojunction)
Taken from [4] JT Verdeyen Laser Electronics Prentice Hall Englewood Cliffs 1995
Edge-emitting laser
17
Typical semiconductor laser
The ideal output power
against current
characteristic
Taken from [11] JM Senior Optical Fiber Communications Prentice Hall New York 1992
18
Threshold gaincurrent
Lets introduce threshold gain coefficient thg
depending on current density
threshold
thth Jg
where β is a constant appropriate to specific devices
Fractional loss Fl of the Fabry ndashPerot cavity is
LRRloss
2exp21
where
- single loss coefficient per unit round trip
Fractional gain of the Fabry ndashPerot cavity is
Lggain
2exp
where g
- single gain coefficient per unit round trip
19
Threshold gaincurrent The threshold case requires
12exp2exp 21 LRRLg
12exp21 LgRR
Hence
21
1ln
2
1
RRLg th
the gain threshold
So we can write
thth Jg
by transformation we can find the threshold value for current density
21
1ln
2
11
RRLJ th
20
Threshold gaincurrent Example
A GaAs injection laser has an optical cavity of length L = 250 μm and widh
w = 100 μm At normal operating temperature the gain factor
β = 21 10-3 [Acm-3] and the loss coefficient
= 10 refractive index n = 36
Assuming R1 = 1 and reflection of mirror 2 3201
12
2
n
nR
The threshold current may be obtain from the equation from the previous slide
2
3
21
106521
ln2
11
cm
A
RRLJ th
The threshold current
mAcavityopticaltheofareaJI thth 663
Taken from [11] JM Senior Optical Fiber Communications Prentice Hall New York 1992
21
Efficiency
Below the threshold laser acts like a LED
Above the threshold stimulated emission
dominates the spontaneous emission
causing laser emission
Formal definition of the efficiency η
For a laser with drive current I and a threshold
current Ithr the output power of the laser at
wavelength λ is
( )thr
hcP I I
e
22
bull More efficient diode lasers are based on heterojunctions
bull Heterojunction is formed between two different semiconductors with different bangap energies
bull Typical materials eg GaAs and AlGaAs
bull One semiconductor is sandwiched between two cladding layers of another semiconductor
Heterojunction lasers
23
Heterojunction laser
AlGaAs (n)
GaAs
Substrate n (GaAs)
AlGaAs (p) 1 μm
1 μm
015 μm
24
LED vs Laser diode
Power vs Current Spectral width
25
Materials amp wavelengths
Taken from Optics and Photonics an introduction 2nd edition Wiley
26
bull Fabry-Perot
bull Distributed Feedback (DFB)
bull Distributed Bragg Reflector (DBR)
bull Grating-stabilized laser
bull External cavity laser (ECL)
Cavities
27
Modes
Taken from [9] F Tragger Ed Springer Handbook of Lasers and Optics Springer New York 2007
28
bull Incorporates the grating within the laser diode structure itself
bull The Bragg grating selects only one mode
bull single-frequency operation over broad temperature and current ranges
bull Tuning 2-4 nm
bull Linewidth 1 ndash 10 MHz
Distributed feedback laser
29
bull The reflector is outsite the active section
bull Broad tuning range possible (up to 40 nm)
bull Mode hopping possible
Distributed Bragg Reflector
30
bull The grating stabilizes the wavelength of the laser (provides a small feedback)
bull Grating is outside the laser (it is not a laser mirror)
bull Might be placed on a fiber
Grating-stabilized lasers
31
External cavity lasers
bull A grating inside allows
wavelength tuning in a
broad range
bull The linewidths are very
narrow
bull bdquoBulkrdquo construction long
resonator
32
bull VCSEL
Surface emitting laser
bull Limited output power
bull Very small resonator
length (few micrometers)
bull Easy achievable single-
frequency operation
bull High modulation
frequency (useful in
telecom)
bull Most common emission
750 ndash 980 nm
33
bull VECSEL (Vertical External-cavity Surface-emitting Laser)
External cavity
34
VECSELs VECSELs enable optical pumping
35
bull TO can
Housings
36
bull C-mount
Housings
37
bull 14-pin Butterfly
Housings
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
15
Electroluminescence (LED)
16
p-n junction laser (homojunction)
Taken from [4] JT Verdeyen Laser Electronics Prentice Hall Englewood Cliffs 1995
Edge-emitting laser
17
Typical semiconductor laser
The ideal output power
against current
characteristic
Taken from [11] JM Senior Optical Fiber Communications Prentice Hall New York 1992
18
Threshold gaincurrent
Lets introduce threshold gain coefficient thg
depending on current density
threshold
thth Jg
where β is a constant appropriate to specific devices
Fractional loss Fl of the Fabry ndashPerot cavity is
LRRloss
2exp21
where
- single loss coefficient per unit round trip
Fractional gain of the Fabry ndashPerot cavity is
Lggain
2exp
where g
- single gain coefficient per unit round trip
19
Threshold gaincurrent The threshold case requires
12exp2exp 21 LRRLg
12exp21 LgRR
Hence
21
1ln
2
1
RRLg th
the gain threshold
So we can write
thth Jg
by transformation we can find the threshold value for current density
21
1ln
2
11
RRLJ th
20
Threshold gaincurrent Example
A GaAs injection laser has an optical cavity of length L = 250 μm and widh
w = 100 μm At normal operating temperature the gain factor
β = 21 10-3 [Acm-3] and the loss coefficient
= 10 refractive index n = 36
Assuming R1 = 1 and reflection of mirror 2 3201
12
2
n
nR
The threshold current may be obtain from the equation from the previous slide
2
3
21
106521
ln2
11
cm
A
RRLJ th
The threshold current
mAcavityopticaltheofareaJI thth 663
Taken from [11] JM Senior Optical Fiber Communications Prentice Hall New York 1992
21
Efficiency
Below the threshold laser acts like a LED
Above the threshold stimulated emission
dominates the spontaneous emission
causing laser emission
Formal definition of the efficiency η
For a laser with drive current I and a threshold
current Ithr the output power of the laser at
wavelength λ is
( )thr
hcP I I
e
22
bull More efficient diode lasers are based on heterojunctions
bull Heterojunction is formed between two different semiconductors with different bangap energies
bull Typical materials eg GaAs and AlGaAs
bull One semiconductor is sandwiched between two cladding layers of another semiconductor
Heterojunction lasers
23
Heterojunction laser
AlGaAs (n)
GaAs
Substrate n (GaAs)
AlGaAs (p) 1 μm
1 μm
015 μm
24
LED vs Laser diode
Power vs Current Spectral width
25
Materials amp wavelengths
Taken from Optics and Photonics an introduction 2nd edition Wiley
26
bull Fabry-Perot
bull Distributed Feedback (DFB)
bull Distributed Bragg Reflector (DBR)
bull Grating-stabilized laser
bull External cavity laser (ECL)
Cavities
27
Modes
Taken from [9] F Tragger Ed Springer Handbook of Lasers and Optics Springer New York 2007
28
bull Incorporates the grating within the laser diode structure itself
bull The Bragg grating selects only one mode
bull single-frequency operation over broad temperature and current ranges
bull Tuning 2-4 nm
bull Linewidth 1 ndash 10 MHz
Distributed feedback laser
29
bull The reflector is outsite the active section
bull Broad tuning range possible (up to 40 nm)
bull Mode hopping possible
Distributed Bragg Reflector
30
bull The grating stabilizes the wavelength of the laser (provides a small feedback)
bull Grating is outside the laser (it is not a laser mirror)
bull Might be placed on a fiber
Grating-stabilized lasers
31
External cavity lasers
bull A grating inside allows
wavelength tuning in a
broad range
bull The linewidths are very
narrow
bull bdquoBulkrdquo construction long
resonator
32
bull VCSEL
Surface emitting laser
bull Limited output power
bull Very small resonator
length (few micrometers)
bull Easy achievable single-
frequency operation
bull High modulation
frequency (useful in
telecom)
bull Most common emission
750 ndash 980 nm
33
bull VECSEL (Vertical External-cavity Surface-emitting Laser)
External cavity
34
VECSELs VECSELs enable optical pumping
35
bull TO can
Housings
36
bull C-mount
Housings
37
bull 14-pin Butterfly
Housings
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
16
p-n junction laser (homojunction)
Taken from [4] JT Verdeyen Laser Electronics Prentice Hall Englewood Cliffs 1995
Edge-emitting laser
17
Typical semiconductor laser
The ideal output power
against current
characteristic
Taken from [11] JM Senior Optical Fiber Communications Prentice Hall New York 1992
18
Threshold gaincurrent
Lets introduce threshold gain coefficient thg
depending on current density
threshold
thth Jg
where β is a constant appropriate to specific devices
Fractional loss Fl of the Fabry ndashPerot cavity is
LRRloss
2exp21
where
- single loss coefficient per unit round trip
Fractional gain of the Fabry ndashPerot cavity is
Lggain
2exp
where g
- single gain coefficient per unit round trip
19
Threshold gaincurrent The threshold case requires
12exp2exp 21 LRRLg
12exp21 LgRR
Hence
21
1ln
2
1
RRLg th
the gain threshold
So we can write
thth Jg
by transformation we can find the threshold value for current density
21
1ln
2
11
RRLJ th
20
Threshold gaincurrent Example
A GaAs injection laser has an optical cavity of length L = 250 μm and widh
w = 100 μm At normal operating temperature the gain factor
β = 21 10-3 [Acm-3] and the loss coefficient
= 10 refractive index n = 36
Assuming R1 = 1 and reflection of mirror 2 3201
12
2
n
nR
The threshold current may be obtain from the equation from the previous slide
2
3
21
106521
ln2
11
cm
A
RRLJ th
The threshold current
mAcavityopticaltheofareaJI thth 663
Taken from [11] JM Senior Optical Fiber Communications Prentice Hall New York 1992
21
Efficiency
Below the threshold laser acts like a LED
Above the threshold stimulated emission
dominates the spontaneous emission
causing laser emission
Formal definition of the efficiency η
For a laser with drive current I and a threshold
current Ithr the output power of the laser at
wavelength λ is
( )thr
hcP I I
e
22
bull More efficient diode lasers are based on heterojunctions
bull Heterojunction is formed between two different semiconductors with different bangap energies
bull Typical materials eg GaAs and AlGaAs
bull One semiconductor is sandwiched between two cladding layers of another semiconductor
Heterojunction lasers
23
Heterojunction laser
AlGaAs (n)
GaAs
Substrate n (GaAs)
AlGaAs (p) 1 μm
1 μm
015 μm
24
LED vs Laser diode
Power vs Current Spectral width
25
Materials amp wavelengths
Taken from Optics and Photonics an introduction 2nd edition Wiley
26
bull Fabry-Perot
bull Distributed Feedback (DFB)
bull Distributed Bragg Reflector (DBR)
bull Grating-stabilized laser
bull External cavity laser (ECL)
Cavities
27
Modes
Taken from [9] F Tragger Ed Springer Handbook of Lasers and Optics Springer New York 2007
28
bull Incorporates the grating within the laser diode structure itself
bull The Bragg grating selects only one mode
bull single-frequency operation over broad temperature and current ranges
bull Tuning 2-4 nm
bull Linewidth 1 ndash 10 MHz
Distributed feedback laser
29
bull The reflector is outsite the active section
bull Broad tuning range possible (up to 40 nm)
bull Mode hopping possible
Distributed Bragg Reflector
30
bull The grating stabilizes the wavelength of the laser (provides a small feedback)
bull Grating is outside the laser (it is not a laser mirror)
bull Might be placed on a fiber
Grating-stabilized lasers
31
External cavity lasers
bull A grating inside allows
wavelength tuning in a
broad range
bull The linewidths are very
narrow
bull bdquoBulkrdquo construction long
resonator
32
bull VCSEL
Surface emitting laser
bull Limited output power
bull Very small resonator
length (few micrometers)
bull Easy achievable single-
frequency operation
bull High modulation
frequency (useful in
telecom)
bull Most common emission
750 ndash 980 nm
33
bull VECSEL (Vertical External-cavity Surface-emitting Laser)
External cavity
34
VECSELs VECSELs enable optical pumping
35
bull TO can
Housings
36
bull C-mount
Housings
37
bull 14-pin Butterfly
Housings
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
17
Typical semiconductor laser
The ideal output power
against current
characteristic
Taken from [11] JM Senior Optical Fiber Communications Prentice Hall New York 1992
18
Threshold gaincurrent
Lets introduce threshold gain coefficient thg
depending on current density
threshold
thth Jg
where β is a constant appropriate to specific devices
Fractional loss Fl of the Fabry ndashPerot cavity is
LRRloss
2exp21
where
- single loss coefficient per unit round trip
Fractional gain of the Fabry ndashPerot cavity is
Lggain
2exp
where g
- single gain coefficient per unit round trip
19
Threshold gaincurrent The threshold case requires
12exp2exp 21 LRRLg
12exp21 LgRR
Hence
21
1ln
2
1
RRLg th
the gain threshold
So we can write
thth Jg
by transformation we can find the threshold value for current density
21
1ln
2
11
RRLJ th
20
Threshold gaincurrent Example
A GaAs injection laser has an optical cavity of length L = 250 μm and widh
w = 100 μm At normal operating temperature the gain factor
β = 21 10-3 [Acm-3] and the loss coefficient
= 10 refractive index n = 36
Assuming R1 = 1 and reflection of mirror 2 3201
12
2
n
nR
The threshold current may be obtain from the equation from the previous slide
2
3
21
106521
ln2
11
cm
A
RRLJ th
The threshold current
mAcavityopticaltheofareaJI thth 663
Taken from [11] JM Senior Optical Fiber Communications Prentice Hall New York 1992
21
Efficiency
Below the threshold laser acts like a LED
Above the threshold stimulated emission
dominates the spontaneous emission
causing laser emission
Formal definition of the efficiency η
For a laser with drive current I and a threshold
current Ithr the output power of the laser at
wavelength λ is
( )thr
hcP I I
e
22
bull More efficient diode lasers are based on heterojunctions
bull Heterojunction is formed between two different semiconductors with different bangap energies
bull Typical materials eg GaAs and AlGaAs
bull One semiconductor is sandwiched between two cladding layers of another semiconductor
Heterojunction lasers
23
Heterojunction laser
AlGaAs (n)
GaAs
Substrate n (GaAs)
AlGaAs (p) 1 μm
1 μm
015 μm
24
LED vs Laser diode
Power vs Current Spectral width
25
Materials amp wavelengths
Taken from Optics and Photonics an introduction 2nd edition Wiley
26
bull Fabry-Perot
bull Distributed Feedback (DFB)
bull Distributed Bragg Reflector (DBR)
bull Grating-stabilized laser
bull External cavity laser (ECL)
Cavities
27
Modes
Taken from [9] F Tragger Ed Springer Handbook of Lasers and Optics Springer New York 2007
28
bull Incorporates the grating within the laser diode structure itself
bull The Bragg grating selects only one mode
bull single-frequency operation over broad temperature and current ranges
bull Tuning 2-4 nm
bull Linewidth 1 ndash 10 MHz
Distributed feedback laser
29
bull The reflector is outsite the active section
bull Broad tuning range possible (up to 40 nm)
bull Mode hopping possible
Distributed Bragg Reflector
30
bull The grating stabilizes the wavelength of the laser (provides a small feedback)
bull Grating is outside the laser (it is not a laser mirror)
bull Might be placed on a fiber
Grating-stabilized lasers
31
External cavity lasers
bull A grating inside allows
wavelength tuning in a
broad range
bull The linewidths are very
narrow
bull bdquoBulkrdquo construction long
resonator
32
bull VCSEL
Surface emitting laser
bull Limited output power
bull Very small resonator
length (few micrometers)
bull Easy achievable single-
frequency operation
bull High modulation
frequency (useful in
telecom)
bull Most common emission
750 ndash 980 nm
33
bull VECSEL (Vertical External-cavity Surface-emitting Laser)
External cavity
34
VECSELs VECSELs enable optical pumping
35
bull TO can
Housings
36
bull C-mount
Housings
37
bull 14-pin Butterfly
Housings
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
18
Threshold gaincurrent
Lets introduce threshold gain coefficient thg
depending on current density
threshold
thth Jg
where β is a constant appropriate to specific devices
Fractional loss Fl of the Fabry ndashPerot cavity is
LRRloss
2exp21
where
- single loss coefficient per unit round trip
Fractional gain of the Fabry ndashPerot cavity is
Lggain
2exp
where g
- single gain coefficient per unit round trip
19
Threshold gaincurrent The threshold case requires
12exp2exp 21 LRRLg
12exp21 LgRR
Hence
21
1ln
2
1
RRLg th
the gain threshold
So we can write
thth Jg
by transformation we can find the threshold value for current density
21
1ln
2
11
RRLJ th
20
Threshold gaincurrent Example
A GaAs injection laser has an optical cavity of length L = 250 μm and widh
w = 100 μm At normal operating temperature the gain factor
β = 21 10-3 [Acm-3] and the loss coefficient
= 10 refractive index n = 36
Assuming R1 = 1 and reflection of mirror 2 3201
12
2
n
nR
The threshold current may be obtain from the equation from the previous slide
2
3
21
106521
ln2
11
cm
A
RRLJ th
The threshold current
mAcavityopticaltheofareaJI thth 663
Taken from [11] JM Senior Optical Fiber Communications Prentice Hall New York 1992
21
Efficiency
Below the threshold laser acts like a LED
Above the threshold stimulated emission
dominates the spontaneous emission
causing laser emission
Formal definition of the efficiency η
For a laser with drive current I and a threshold
current Ithr the output power of the laser at
wavelength λ is
( )thr
hcP I I
e
22
bull More efficient diode lasers are based on heterojunctions
bull Heterojunction is formed between two different semiconductors with different bangap energies
bull Typical materials eg GaAs and AlGaAs
bull One semiconductor is sandwiched between two cladding layers of another semiconductor
Heterojunction lasers
23
Heterojunction laser
AlGaAs (n)
GaAs
Substrate n (GaAs)
AlGaAs (p) 1 μm
1 μm
015 μm
24
LED vs Laser diode
Power vs Current Spectral width
25
Materials amp wavelengths
Taken from Optics and Photonics an introduction 2nd edition Wiley
26
bull Fabry-Perot
bull Distributed Feedback (DFB)
bull Distributed Bragg Reflector (DBR)
bull Grating-stabilized laser
bull External cavity laser (ECL)
Cavities
27
Modes
Taken from [9] F Tragger Ed Springer Handbook of Lasers and Optics Springer New York 2007
28
bull Incorporates the grating within the laser diode structure itself
bull The Bragg grating selects only one mode
bull single-frequency operation over broad temperature and current ranges
bull Tuning 2-4 nm
bull Linewidth 1 ndash 10 MHz
Distributed feedback laser
29
bull The reflector is outsite the active section
bull Broad tuning range possible (up to 40 nm)
bull Mode hopping possible
Distributed Bragg Reflector
30
bull The grating stabilizes the wavelength of the laser (provides a small feedback)
bull Grating is outside the laser (it is not a laser mirror)
bull Might be placed on a fiber
Grating-stabilized lasers
31
External cavity lasers
bull A grating inside allows
wavelength tuning in a
broad range
bull The linewidths are very
narrow
bull bdquoBulkrdquo construction long
resonator
32
bull VCSEL
Surface emitting laser
bull Limited output power
bull Very small resonator
length (few micrometers)
bull Easy achievable single-
frequency operation
bull High modulation
frequency (useful in
telecom)
bull Most common emission
750 ndash 980 nm
33
bull VECSEL (Vertical External-cavity Surface-emitting Laser)
External cavity
34
VECSELs VECSELs enable optical pumping
35
bull TO can
Housings
36
bull C-mount
Housings
37
bull 14-pin Butterfly
Housings
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
19
Threshold gaincurrent The threshold case requires
12exp2exp 21 LRRLg
12exp21 LgRR
Hence
21
1ln
2
1
RRLg th
the gain threshold
So we can write
thth Jg
by transformation we can find the threshold value for current density
21
1ln
2
11
RRLJ th
20
Threshold gaincurrent Example
A GaAs injection laser has an optical cavity of length L = 250 μm and widh
w = 100 μm At normal operating temperature the gain factor
β = 21 10-3 [Acm-3] and the loss coefficient
= 10 refractive index n = 36
Assuming R1 = 1 and reflection of mirror 2 3201
12
2
n
nR
The threshold current may be obtain from the equation from the previous slide
2
3
21
106521
ln2
11
cm
A
RRLJ th
The threshold current
mAcavityopticaltheofareaJI thth 663
Taken from [11] JM Senior Optical Fiber Communications Prentice Hall New York 1992
21
Efficiency
Below the threshold laser acts like a LED
Above the threshold stimulated emission
dominates the spontaneous emission
causing laser emission
Formal definition of the efficiency η
For a laser with drive current I and a threshold
current Ithr the output power of the laser at
wavelength λ is
( )thr
hcP I I
e
22
bull More efficient diode lasers are based on heterojunctions
bull Heterojunction is formed between two different semiconductors with different bangap energies
bull Typical materials eg GaAs and AlGaAs
bull One semiconductor is sandwiched between two cladding layers of another semiconductor
Heterojunction lasers
23
Heterojunction laser
AlGaAs (n)
GaAs
Substrate n (GaAs)
AlGaAs (p) 1 μm
1 μm
015 μm
24
LED vs Laser diode
Power vs Current Spectral width
25
Materials amp wavelengths
Taken from Optics and Photonics an introduction 2nd edition Wiley
26
bull Fabry-Perot
bull Distributed Feedback (DFB)
bull Distributed Bragg Reflector (DBR)
bull Grating-stabilized laser
bull External cavity laser (ECL)
Cavities
27
Modes
Taken from [9] F Tragger Ed Springer Handbook of Lasers and Optics Springer New York 2007
28
bull Incorporates the grating within the laser diode structure itself
bull The Bragg grating selects only one mode
bull single-frequency operation over broad temperature and current ranges
bull Tuning 2-4 nm
bull Linewidth 1 ndash 10 MHz
Distributed feedback laser
29
bull The reflector is outsite the active section
bull Broad tuning range possible (up to 40 nm)
bull Mode hopping possible
Distributed Bragg Reflector
30
bull The grating stabilizes the wavelength of the laser (provides a small feedback)
bull Grating is outside the laser (it is not a laser mirror)
bull Might be placed on a fiber
Grating-stabilized lasers
31
External cavity lasers
bull A grating inside allows
wavelength tuning in a
broad range
bull The linewidths are very
narrow
bull bdquoBulkrdquo construction long
resonator
32
bull VCSEL
Surface emitting laser
bull Limited output power
bull Very small resonator
length (few micrometers)
bull Easy achievable single-
frequency operation
bull High modulation
frequency (useful in
telecom)
bull Most common emission
750 ndash 980 nm
33
bull VECSEL (Vertical External-cavity Surface-emitting Laser)
External cavity
34
VECSELs VECSELs enable optical pumping
35
bull TO can
Housings
36
bull C-mount
Housings
37
bull 14-pin Butterfly
Housings
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
20
Threshold gaincurrent Example
A GaAs injection laser has an optical cavity of length L = 250 μm and widh
w = 100 μm At normal operating temperature the gain factor
β = 21 10-3 [Acm-3] and the loss coefficient
= 10 refractive index n = 36
Assuming R1 = 1 and reflection of mirror 2 3201
12
2
n
nR
The threshold current may be obtain from the equation from the previous slide
2
3
21
106521
ln2
11
cm
A
RRLJ th
The threshold current
mAcavityopticaltheofareaJI thth 663
Taken from [11] JM Senior Optical Fiber Communications Prentice Hall New York 1992
21
Efficiency
Below the threshold laser acts like a LED
Above the threshold stimulated emission
dominates the spontaneous emission
causing laser emission
Formal definition of the efficiency η
For a laser with drive current I and a threshold
current Ithr the output power of the laser at
wavelength λ is
( )thr
hcP I I
e
22
bull More efficient diode lasers are based on heterojunctions
bull Heterojunction is formed between two different semiconductors with different bangap energies
bull Typical materials eg GaAs and AlGaAs
bull One semiconductor is sandwiched between two cladding layers of another semiconductor
Heterojunction lasers
23
Heterojunction laser
AlGaAs (n)
GaAs
Substrate n (GaAs)
AlGaAs (p) 1 μm
1 μm
015 μm
24
LED vs Laser diode
Power vs Current Spectral width
25
Materials amp wavelengths
Taken from Optics and Photonics an introduction 2nd edition Wiley
26
bull Fabry-Perot
bull Distributed Feedback (DFB)
bull Distributed Bragg Reflector (DBR)
bull Grating-stabilized laser
bull External cavity laser (ECL)
Cavities
27
Modes
Taken from [9] F Tragger Ed Springer Handbook of Lasers and Optics Springer New York 2007
28
bull Incorporates the grating within the laser diode structure itself
bull The Bragg grating selects only one mode
bull single-frequency operation over broad temperature and current ranges
bull Tuning 2-4 nm
bull Linewidth 1 ndash 10 MHz
Distributed feedback laser
29
bull The reflector is outsite the active section
bull Broad tuning range possible (up to 40 nm)
bull Mode hopping possible
Distributed Bragg Reflector
30
bull The grating stabilizes the wavelength of the laser (provides a small feedback)
bull Grating is outside the laser (it is not a laser mirror)
bull Might be placed on a fiber
Grating-stabilized lasers
31
External cavity lasers
bull A grating inside allows
wavelength tuning in a
broad range
bull The linewidths are very
narrow
bull bdquoBulkrdquo construction long
resonator
32
bull VCSEL
Surface emitting laser
bull Limited output power
bull Very small resonator
length (few micrometers)
bull Easy achievable single-
frequency operation
bull High modulation
frequency (useful in
telecom)
bull Most common emission
750 ndash 980 nm
33
bull VECSEL (Vertical External-cavity Surface-emitting Laser)
External cavity
34
VECSELs VECSELs enable optical pumping
35
bull TO can
Housings
36
bull C-mount
Housings
37
bull 14-pin Butterfly
Housings
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
21
Efficiency
Below the threshold laser acts like a LED
Above the threshold stimulated emission
dominates the spontaneous emission
causing laser emission
Formal definition of the efficiency η
For a laser with drive current I and a threshold
current Ithr the output power of the laser at
wavelength λ is
( )thr
hcP I I
e
22
bull More efficient diode lasers are based on heterojunctions
bull Heterojunction is formed between two different semiconductors with different bangap energies
bull Typical materials eg GaAs and AlGaAs
bull One semiconductor is sandwiched between two cladding layers of another semiconductor
Heterojunction lasers
23
Heterojunction laser
AlGaAs (n)
GaAs
Substrate n (GaAs)
AlGaAs (p) 1 μm
1 μm
015 μm
24
LED vs Laser diode
Power vs Current Spectral width
25
Materials amp wavelengths
Taken from Optics and Photonics an introduction 2nd edition Wiley
26
bull Fabry-Perot
bull Distributed Feedback (DFB)
bull Distributed Bragg Reflector (DBR)
bull Grating-stabilized laser
bull External cavity laser (ECL)
Cavities
27
Modes
Taken from [9] F Tragger Ed Springer Handbook of Lasers and Optics Springer New York 2007
28
bull Incorporates the grating within the laser diode structure itself
bull The Bragg grating selects only one mode
bull single-frequency operation over broad temperature and current ranges
bull Tuning 2-4 nm
bull Linewidth 1 ndash 10 MHz
Distributed feedback laser
29
bull The reflector is outsite the active section
bull Broad tuning range possible (up to 40 nm)
bull Mode hopping possible
Distributed Bragg Reflector
30
bull The grating stabilizes the wavelength of the laser (provides a small feedback)
bull Grating is outside the laser (it is not a laser mirror)
bull Might be placed on a fiber
Grating-stabilized lasers
31
External cavity lasers
bull A grating inside allows
wavelength tuning in a
broad range
bull The linewidths are very
narrow
bull bdquoBulkrdquo construction long
resonator
32
bull VCSEL
Surface emitting laser
bull Limited output power
bull Very small resonator
length (few micrometers)
bull Easy achievable single-
frequency operation
bull High modulation
frequency (useful in
telecom)
bull Most common emission
750 ndash 980 nm
33
bull VECSEL (Vertical External-cavity Surface-emitting Laser)
External cavity
34
VECSELs VECSELs enable optical pumping
35
bull TO can
Housings
36
bull C-mount
Housings
37
bull 14-pin Butterfly
Housings
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
22
bull More efficient diode lasers are based on heterojunctions
bull Heterojunction is formed between two different semiconductors with different bangap energies
bull Typical materials eg GaAs and AlGaAs
bull One semiconductor is sandwiched between two cladding layers of another semiconductor
Heterojunction lasers
23
Heterojunction laser
AlGaAs (n)
GaAs
Substrate n (GaAs)
AlGaAs (p) 1 μm
1 μm
015 μm
24
LED vs Laser diode
Power vs Current Spectral width
25
Materials amp wavelengths
Taken from Optics and Photonics an introduction 2nd edition Wiley
26
bull Fabry-Perot
bull Distributed Feedback (DFB)
bull Distributed Bragg Reflector (DBR)
bull Grating-stabilized laser
bull External cavity laser (ECL)
Cavities
27
Modes
Taken from [9] F Tragger Ed Springer Handbook of Lasers and Optics Springer New York 2007
28
bull Incorporates the grating within the laser diode structure itself
bull The Bragg grating selects only one mode
bull single-frequency operation over broad temperature and current ranges
bull Tuning 2-4 nm
bull Linewidth 1 ndash 10 MHz
Distributed feedback laser
29
bull The reflector is outsite the active section
bull Broad tuning range possible (up to 40 nm)
bull Mode hopping possible
Distributed Bragg Reflector
30
bull The grating stabilizes the wavelength of the laser (provides a small feedback)
bull Grating is outside the laser (it is not a laser mirror)
bull Might be placed on a fiber
Grating-stabilized lasers
31
External cavity lasers
bull A grating inside allows
wavelength tuning in a
broad range
bull The linewidths are very
narrow
bull bdquoBulkrdquo construction long
resonator
32
bull VCSEL
Surface emitting laser
bull Limited output power
bull Very small resonator
length (few micrometers)
bull Easy achievable single-
frequency operation
bull High modulation
frequency (useful in
telecom)
bull Most common emission
750 ndash 980 nm
33
bull VECSEL (Vertical External-cavity Surface-emitting Laser)
External cavity
34
VECSELs VECSELs enable optical pumping
35
bull TO can
Housings
36
bull C-mount
Housings
37
bull 14-pin Butterfly
Housings
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
23
Heterojunction laser
AlGaAs (n)
GaAs
Substrate n (GaAs)
AlGaAs (p) 1 μm
1 μm
015 μm
24
LED vs Laser diode
Power vs Current Spectral width
25
Materials amp wavelengths
Taken from Optics and Photonics an introduction 2nd edition Wiley
26
bull Fabry-Perot
bull Distributed Feedback (DFB)
bull Distributed Bragg Reflector (DBR)
bull Grating-stabilized laser
bull External cavity laser (ECL)
Cavities
27
Modes
Taken from [9] F Tragger Ed Springer Handbook of Lasers and Optics Springer New York 2007
28
bull Incorporates the grating within the laser diode structure itself
bull The Bragg grating selects only one mode
bull single-frequency operation over broad temperature and current ranges
bull Tuning 2-4 nm
bull Linewidth 1 ndash 10 MHz
Distributed feedback laser
29
bull The reflector is outsite the active section
bull Broad tuning range possible (up to 40 nm)
bull Mode hopping possible
Distributed Bragg Reflector
30
bull The grating stabilizes the wavelength of the laser (provides a small feedback)
bull Grating is outside the laser (it is not a laser mirror)
bull Might be placed on a fiber
Grating-stabilized lasers
31
External cavity lasers
bull A grating inside allows
wavelength tuning in a
broad range
bull The linewidths are very
narrow
bull bdquoBulkrdquo construction long
resonator
32
bull VCSEL
Surface emitting laser
bull Limited output power
bull Very small resonator
length (few micrometers)
bull Easy achievable single-
frequency operation
bull High modulation
frequency (useful in
telecom)
bull Most common emission
750 ndash 980 nm
33
bull VECSEL (Vertical External-cavity Surface-emitting Laser)
External cavity
34
VECSELs VECSELs enable optical pumping
35
bull TO can
Housings
36
bull C-mount
Housings
37
bull 14-pin Butterfly
Housings
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
24
LED vs Laser diode
Power vs Current Spectral width
25
Materials amp wavelengths
Taken from Optics and Photonics an introduction 2nd edition Wiley
26
bull Fabry-Perot
bull Distributed Feedback (DFB)
bull Distributed Bragg Reflector (DBR)
bull Grating-stabilized laser
bull External cavity laser (ECL)
Cavities
27
Modes
Taken from [9] F Tragger Ed Springer Handbook of Lasers and Optics Springer New York 2007
28
bull Incorporates the grating within the laser diode structure itself
bull The Bragg grating selects only one mode
bull single-frequency operation over broad temperature and current ranges
bull Tuning 2-4 nm
bull Linewidth 1 ndash 10 MHz
Distributed feedback laser
29
bull The reflector is outsite the active section
bull Broad tuning range possible (up to 40 nm)
bull Mode hopping possible
Distributed Bragg Reflector
30
bull The grating stabilizes the wavelength of the laser (provides a small feedback)
bull Grating is outside the laser (it is not a laser mirror)
bull Might be placed on a fiber
Grating-stabilized lasers
31
External cavity lasers
bull A grating inside allows
wavelength tuning in a
broad range
bull The linewidths are very
narrow
bull bdquoBulkrdquo construction long
resonator
32
bull VCSEL
Surface emitting laser
bull Limited output power
bull Very small resonator
length (few micrometers)
bull Easy achievable single-
frequency operation
bull High modulation
frequency (useful in
telecom)
bull Most common emission
750 ndash 980 nm
33
bull VECSEL (Vertical External-cavity Surface-emitting Laser)
External cavity
34
VECSELs VECSELs enable optical pumping
35
bull TO can
Housings
36
bull C-mount
Housings
37
bull 14-pin Butterfly
Housings
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
25
Materials amp wavelengths
Taken from Optics and Photonics an introduction 2nd edition Wiley
26
bull Fabry-Perot
bull Distributed Feedback (DFB)
bull Distributed Bragg Reflector (DBR)
bull Grating-stabilized laser
bull External cavity laser (ECL)
Cavities
27
Modes
Taken from [9] F Tragger Ed Springer Handbook of Lasers and Optics Springer New York 2007
28
bull Incorporates the grating within the laser diode structure itself
bull The Bragg grating selects only one mode
bull single-frequency operation over broad temperature and current ranges
bull Tuning 2-4 nm
bull Linewidth 1 ndash 10 MHz
Distributed feedback laser
29
bull The reflector is outsite the active section
bull Broad tuning range possible (up to 40 nm)
bull Mode hopping possible
Distributed Bragg Reflector
30
bull The grating stabilizes the wavelength of the laser (provides a small feedback)
bull Grating is outside the laser (it is not a laser mirror)
bull Might be placed on a fiber
Grating-stabilized lasers
31
External cavity lasers
bull A grating inside allows
wavelength tuning in a
broad range
bull The linewidths are very
narrow
bull bdquoBulkrdquo construction long
resonator
32
bull VCSEL
Surface emitting laser
bull Limited output power
bull Very small resonator
length (few micrometers)
bull Easy achievable single-
frequency operation
bull High modulation
frequency (useful in
telecom)
bull Most common emission
750 ndash 980 nm
33
bull VECSEL (Vertical External-cavity Surface-emitting Laser)
External cavity
34
VECSELs VECSELs enable optical pumping
35
bull TO can
Housings
36
bull C-mount
Housings
37
bull 14-pin Butterfly
Housings
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
26
bull Fabry-Perot
bull Distributed Feedback (DFB)
bull Distributed Bragg Reflector (DBR)
bull Grating-stabilized laser
bull External cavity laser (ECL)
Cavities
27
Modes
Taken from [9] F Tragger Ed Springer Handbook of Lasers and Optics Springer New York 2007
28
bull Incorporates the grating within the laser diode structure itself
bull The Bragg grating selects only one mode
bull single-frequency operation over broad temperature and current ranges
bull Tuning 2-4 nm
bull Linewidth 1 ndash 10 MHz
Distributed feedback laser
29
bull The reflector is outsite the active section
bull Broad tuning range possible (up to 40 nm)
bull Mode hopping possible
Distributed Bragg Reflector
30
bull The grating stabilizes the wavelength of the laser (provides a small feedback)
bull Grating is outside the laser (it is not a laser mirror)
bull Might be placed on a fiber
Grating-stabilized lasers
31
External cavity lasers
bull A grating inside allows
wavelength tuning in a
broad range
bull The linewidths are very
narrow
bull bdquoBulkrdquo construction long
resonator
32
bull VCSEL
Surface emitting laser
bull Limited output power
bull Very small resonator
length (few micrometers)
bull Easy achievable single-
frequency operation
bull High modulation
frequency (useful in
telecom)
bull Most common emission
750 ndash 980 nm
33
bull VECSEL (Vertical External-cavity Surface-emitting Laser)
External cavity
34
VECSELs VECSELs enable optical pumping
35
bull TO can
Housings
36
bull C-mount
Housings
37
bull 14-pin Butterfly
Housings
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
27
Modes
Taken from [9] F Tragger Ed Springer Handbook of Lasers and Optics Springer New York 2007
28
bull Incorporates the grating within the laser diode structure itself
bull The Bragg grating selects only one mode
bull single-frequency operation over broad temperature and current ranges
bull Tuning 2-4 nm
bull Linewidth 1 ndash 10 MHz
Distributed feedback laser
29
bull The reflector is outsite the active section
bull Broad tuning range possible (up to 40 nm)
bull Mode hopping possible
Distributed Bragg Reflector
30
bull The grating stabilizes the wavelength of the laser (provides a small feedback)
bull Grating is outside the laser (it is not a laser mirror)
bull Might be placed on a fiber
Grating-stabilized lasers
31
External cavity lasers
bull A grating inside allows
wavelength tuning in a
broad range
bull The linewidths are very
narrow
bull bdquoBulkrdquo construction long
resonator
32
bull VCSEL
Surface emitting laser
bull Limited output power
bull Very small resonator
length (few micrometers)
bull Easy achievable single-
frequency operation
bull High modulation
frequency (useful in
telecom)
bull Most common emission
750 ndash 980 nm
33
bull VECSEL (Vertical External-cavity Surface-emitting Laser)
External cavity
34
VECSELs VECSELs enable optical pumping
35
bull TO can
Housings
36
bull C-mount
Housings
37
bull 14-pin Butterfly
Housings
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
28
bull Incorporates the grating within the laser diode structure itself
bull The Bragg grating selects only one mode
bull single-frequency operation over broad temperature and current ranges
bull Tuning 2-4 nm
bull Linewidth 1 ndash 10 MHz
Distributed feedback laser
29
bull The reflector is outsite the active section
bull Broad tuning range possible (up to 40 nm)
bull Mode hopping possible
Distributed Bragg Reflector
30
bull The grating stabilizes the wavelength of the laser (provides a small feedback)
bull Grating is outside the laser (it is not a laser mirror)
bull Might be placed on a fiber
Grating-stabilized lasers
31
External cavity lasers
bull A grating inside allows
wavelength tuning in a
broad range
bull The linewidths are very
narrow
bull bdquoBulkrdquo construction long
resonator
32
bull VCSEL
Surface emitting laser
bull Limited output power
bull Very small resonator
length (few micrometers)
bull Easy achievable single-
frequency operation
bull High modulation
frequency (useful in
telecom)
bull Most common emission
750 ndash 980 nm
33
bull VECSEL (Vertical External-cavity Surface-emitting Laser)
External cavity
34
VECSELs VECSELs enable optical pumping
35
bull TO can
Housings
36
bull C-mount
Housings
37
bull 14-pin Butterfly
Housings
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
29
bull The reflector is outsite the active section
bull Broad tuning range possible (up to 40 nm)
bull Mode hopping possible
Distributed Bragg Reflector
30
bull The grating stabilizes the wavelength of the laser (provides a small feedback)
bull Grating is outside the laser (it is not a laser mirror)
bull Might be placed on a fiber
Grating-stabilized lasers
31
External cavity lasers
bull A grating inside allows
wavelength tuning in a
broad range
bull The linewidths are very
narrow
bull bdquoBulkrdquo construction long
resonator
32
bull VCSEL
Surface emitting laser
bull Limited output power
bull Very small resonator
length (few micrometers)
bull Easy achievable single-
frequency operation
bull High modulation
frequency (useful in
telecom)
bull Most common emission
750 ndash 980 nm
33
bull VECSEL (Vertical External-cavity Surface-emitting Laser)
External cavity
34
VECSELs VECSELs enable optical pumping
35
bull TO can
Housings
36
bull C-mount
Housings
37
bull 14-pin Butterfly
Housings
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
30
bull The grating stabilizes the wavelength of the laser (provides a small feedback)
bull Grating is outside the laser (it is not a laser mirror)
bull Might be placed on a fiber
Grating-stabilized lasers
31
External cavity lasers
bull A grating inside allows
wavelength tuning in a
broad range
bull The linewidths are very
narrow
bull bdquoBulkrdquo construction long
resonator
32
bull VCSEL
Surface emitting laser
bull Limited output power
bull Very small resonator
length (few micrometers)
bull Easy achievable single-
frequency operation
bull High modulation
frequency (useful in
telecom)
bull Most common emission
750 ndash 980 nm
33
bull VECSEL (Vertical External-cavity Surface-emitting Laser)
External cavity
34
VECSELs VECSELs enable optical pumping
35
bull TO can
Housings
36
bull C-mount
Housings
37
bull 14-pin Butterfly
Housings
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
31
External cavity lasers
bull A grating inside allows
wavelength tuning in a
broad range
bull The linewidths are very
narrow
bull bdquoBulkrdquo construction long
resonator
32
bull VCSEL
Surface emitting laser
bull Limited output power
bull Very small resonator
length (few micrometers)
bull Easy achievable single-
frequency operation
bull High modulation
frequency (useful in
telecom)
bull Most common emission
750 ndash 980 nm
33
bull VECSEL (Vertical External-cavity Surface-emitting Laser)
External cavity
34
VECSELs VECSELs enable optical pumping
35
bull TO can
Housings
36
bull C-mount
Housings
37
bull 14-pin Butterfly
Housings
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
32
bull VCSEL
Surface emitting laser
bull Limited output power
bull Very small resonator
length (few micrometers)
bull Easy achievable single-
frequency operation
bull High modulation
frequency (useful in
telecom)
bull Most common emission
750 ndash 980 nm
33
bull VECSEL (Vertical External-cavity Surface-emitting Laser)
External cavity
34
VECSELs VECSELs enable optical pumping
35
bull TO can
Housings
36
bull C-mount
Housings
37
bull 14-pin Butterfly
Housings
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
33
bull VECSEL (Vertical External-cavity Surface-emitting Laser)
External cavity
34
VECSELs VECSELs enable optical pumping
35
bull TO can
Housings
36
bull C-mount
Housings
37
bull 14-pin Butterfly
Housings
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
34
VECSELs VECSELs enable optical pumping
35
bull TO can
Housings
36
bull C-mount
Housings
37
bull 14-pin Butterfly
Housings
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
35
bull TO can
Housings
36
bull C-mount
Housings
37
bull 14-pin Butterfly
Housings
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
36
bull C-mount
Housings
37
bull 14-pin Butterfly
Housings
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
37
bull 14-pin Butterfly
Housings
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
38
Butterfly - types
Type 1 ndash pump laser Type 2 ndash signal laser
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
39
Butterfly with bias-T
Function
generator
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
40
bull Diodes might be coupled with single-mode or multi-mode fibers
bull The fiber type limits the available output power
bull For single-mode fibers up to 1 W
bull Multimode fibers hundreds of watts
Multimode amp singlemode lasers
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
41
Mid-infrared lasers
bull Quantum Cascade Lasers (QCLs)
bull Interband Cascade Lasers (ICLs)
bull Usually DFB resonator
bull Single-mode operation
bull Custom wavelengths
bull Emission from 6000 nm to 15000 nm
bull Used in sensing spectroscopy
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
42
Quantum Cascade Laser
Taken from the lecture of Jerome Faist Europhoton Conference Lozanna 2004
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
43
QCLs
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
44
QCL example
Nanoplus GmbH
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
45
bull Stable current sources for driving laser diodes and thermoelectric coolers
bull Tabletop devices available on the market (up to 20A)
Laser diode drivers
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
46
OEM modules
Example Thorlabs MLD203CHB
bull 200 mA current
bull 3 V voltage
bull Soft-start
bull 17x10mm package
Example Wavelength Electronics FL500
bull 500 mA current
bull 2 V voltage
bull Soft-start
bull 500 kHz modulation
bull 15x12 mm size
47
OEM driver module
47
OEM driver module