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Winter College on Optics: Fundamentals of Photonics - Theory, Devices and Applications
A. Melloni
10 - 21 February 2014
Dip. Elettronica, Informazione e Bioingegneria Politecnico di Milano
Italy
(Waveguide theory and) photonic circuit design
7th Optoelectronics & Photonics Winter School: Physics and Applications of Optical Resonators – A. Melloni, Politecnico di Milano
(Waveguide theory and) photonic circuit design
A. MelloniDip. Elettronica, Informazione e Bioingegneria
Politecnico di Milano, Italy
Winter College on Optics: Fundamentals of Photonics Theory, Devices and Applications
7th Optoelectronics & Photonics Winter School: Physics and Applications of Optical Resonators – A. Melloni, Politecnico di Milano
Waveguide theory and photonic circuit design
- Waveguides (no theory…)- The role of index contrast in waveguides (survey of technologies, type of
waveguides, index contrast…)- Bends and advanced topics on bends (the matched bend,...)
- The dark side of integrated optical waveguides (backscatter, xtalk, losses, spurious modes, the (ng-neff) role….)
- An excursus on ring resonators: history, spectral characteristics, applications, ...
- Circuits: MZ, rings, higher order filters, delay lines, …- The circuit approach (building Blocks, Circuit simulators and few slides on Aspic, our circuit simulator that will be used at the end of the course for
hands-on session).- The structure of generic foundries and available generic foundries
A. Melloni
Let’s combine rings
ORES School, Levico, 2013 A. Melloni
from Ring to Rings…
A. Yariv Caltech 1999 Microwave
C. Madsen Bell Labs 1999 DSP
R. Orta Politecnico Torino 1999 DSP
A. Melloni Politecnico Milano 2002 Microwave
V. Van Maryland Univ. 2006 Electronic/Microwave
Books from I. Chremmos, O. Schwelb, D.G. Rabus, J. Hebneer, ….
ORES School, Levico, 2013 A. Melloni
from Ring to Rings…
Parallel coupled bandstop filter
Directly coupled bandpass filter (CROW)
Ring-loaded Mach-Zehnder filter
ORES School, Levico, 2013 A. Melloni
Ring loaded Mach-Zehnder
FSR
2N
2(N+1)
APF allows to shape the phase response
1()
2()
ORES School, Levico, 2013 A. Melloni
Tunable bandwidth filterTunable bandwidth filter
kckc
kr
Lr Lr
kr
Bandwidth tunability is obtained by varying
FSR = 200 GHz
B = 23 GHz … 175 GHz
IL < 0.6 dB
ER > -18 dB
ORES School, Levico, 2013 A. Melloni
Coupled resonatorsCoupled resonators
8
ORES School, Levico, 2013 A. Melloni
Direct coupled cavities vs cascaded cavities
Direct coupled cavities(CROW)
-1 -0.5 0 0.5 1-25
-20
-15
-10
-5
0
Frequency
Tran
smis
sion
[dB
] 1
25
Cascaded cavities(SCISSOR)
-1 -0.5 0 0.5 1-25
-20
-15
-10
-5
0
Frequency
Tran
smis
sion
[dB
]
1
25
ORES School, Levico, 2013 A. Melloni
-1.5 -1 -0.5 0 0.5 1 1.5x 104
-50
-40
-30
-20
-10
0
Tran
smis
sion
[dB
]
Frequency [GHz]
B=22THz
-1.5 -1 -0.5 0 0.5 1 1.5x 104
-50
-40
-30
-20
-10
0
Tran
smis
sion
[dB]
Frequency [GHz]
B=22THz
-1500 -1000 -500 0 500 1000 1500-5
-4
-3
-2
-1
0
Tran
smis
sion
[dB]
Frequency [GHz]
K=0.01
1st order cavity d=/2
B1 cavity=1.2 THz
BCROW=22.5 THz
10 cavities 100 cavities
1 cavity
B=1.2THz
Identical cavities ?
ORES School, Levico, 2013 A. Melloni
/4
CROW
Frequency [GHz]
|H(f)|2
[dB]
-14 dB 0 dB
CROW impedance matching
11
ZW neff
ZCROW 2ng ()
Quarter-wavematching
No impedance matching
neff( / 4 ) neff 2ng
ORES School, Levico, 2013 A. Melloni
Impedance Matching (Apodization)
ZW neffZCROW 2ng ()
Quarter-wavematching
No impedancematching
neff( / 4 ) neff 2ng
...
ORES School, Levico, 2013 A. Melloni
IN
THROUGH
Coupled ring resonators
DROP
f0 f0 f0 f0 f0 f0
K0
K1 K2 K3 K2 K1
K0
ProgressProgress in tuneable ringin tuneable ring--CROW CROW
2010
2009
2008
2007
2009
ORES School, Levico, 2013 A. Melloni
N x 40 μm
56 μ
m
F. Morichetti et al., The first decade of coupled resonator optical waveguides: bringing slow light to applications.
Laser & Photonics Reviews, 6: 74–96 (2012)
A. Melloni
Wavelength [nm]
Inte
nsit
y [d
Bm]
Return loss: -15 dB; IL 0.5 dB; In-band ripple <0.2 dB; Off-band rejection >50 dB
8-rings Bandpass filters in SOI
A. Melloni
8-rings Bandpass filters in SOI
Wavelength [nm]6 8 10 12 14 16 18 20 22 10-1210-11
10-1010-910-810-7
10-6
10-5
10-4
10-3
10-2
OSNR over 0.2 nm
BER
Waveguide
λ=1536.27 nmλ=1550.42 nm
λ=1564.75 nm
ORES School, Levico, 2013 A. Melloni
Thermal tuning
8 rings
7 rings
6 rings
5 rings
4 rings
3 rings
1556 1558 1560 1562 1564 1566
-70
-60
-50
-40
-30
-20
Wavelength [nm]
Tran
smis
sion
[dB]
Si
Si
SiO2
Spin‐on glass
w
h
wh
NiCr Au
Thermal crosstalk
=2.5 nm
7 m
28° C 0.7° C
hot ring
cold ring
=0.06 nm
A. Melloni
Tunable Delay lines
ORES School, Levico, 2013 A. Melloni
On-Chip Tunable delay… not an easy task !!!
Electronic
Microwave
Photonics - let photons run around (coil of fiber)
– slow down photons
out
ORES School, Levico, 2013 A. Melloni
Recirculating buffer
Technologies: 2007 Glass for the spire + InP for the switch2010 All Silicon (15 dB/ns)
Spires
Switches
Trade off between waveguide attenuation and switch ER (limit)
Discrete delay line, Packet(s) delay and Buffer
Courtesy of John Bowers, University of California, Santa Barbara INTEL 2010
ORES School, Levico, 2013 A. Melloni
Slow down photons
velocity c
group refractive index
ng of the material: Atomic resonances, band edge, EIT, CPO,…
ng of the circuit: Resonators, Bragg Gratings, Photonic Crystals, Brillouin and Raman,…
Tran
smis
sion
ORES School, Levico, 2013 A. Melloni
Slow down photons
ORES School, Levico, 2013 A. Melloni
Tunable Delay lines
IN
OUT
open ringsclosed rings
λr = λin λr ≠ λin
F. Morichetti et al., Optics Express, Vol. 15, 25, December 2007A. Canciamilla et al., Journal of Optics, IOP, 2010A. Melloni et al., IEEE Photonics Journal, vol. 1, no. 4, 2010
1 byte continuously tuneable delay at 10 and 100 Gbit/s demonstrated
ORES School, Levico, 2013 A. Melloni
-200 -100 0 100 200 300 400 500
0
0.2
0.4
0.6
0.8
1
Inte
nsit
y
Time [ps]
In
In
Locked rings(off-resonance)
Out
in
r ≠in
Minimum delay
The CROW in reflection
-20 -15 -10 -5 0 5 10 15 200
50
100
150
200
250
300
350
Frequency [GHz]Frequency [GHz]
Del
ay [p
s]
ORES School, Levico, 2013 A. Melloni
-200 -100 0 100 200 300 400 500
0
0.2
0.4
0.6
0.8
1
Inte
nsit
y
Time [ps]
20In
In
Out
M = 2
Open rings(on-resonance)
Locked rings(off-resonance)
r ≠in
in
Frequency [GHz]
Del
ay [p
s]
The CROW in reflection
ORES School, Levico, 2013 A. Melloni
-200 -100 0 100 200 300 400 500
0
0.2
0.4
0.6
0.8
1
Inte
nsit
y
Time [ps]
4
0
2
In
In
Out
M = 4
r ≠in
Open rings(on-resonance)
Locked rings(off-resonance)in
F. Morichetti et al., Optics Express, no. 25, Dec. 2007
R-CROW: a reconfigurable delay line
Frequency [GHz]
Del
ay [p
s]
ORES School, Levico, 2013 A. Melloni
R-CROW continuous tuning
ORES School, Levico, 2013 A. Melloni
In
100 ps Intensity modulationOOK NRZ @ 10 Gbit/s
Data transmission at 10 Data transmission at 10 Gbit/sGbit/s
OutReconfiguration
- hitless- time 100 s- power 5 mW
ORES School, Levico, 2013 A. Melloni
0 20 40 60 80 100 1200
1
0.8
0.6
0.4
0.2
TuneableTuneable pulse delay @100Gbit/spulse delay @100Gbit/s
Delay [ps]
Nor
mal
ized
inte
nsit
y
Fractional delay = 7.5 ps/RR
9 ps
11 ps
89 ps (8 bits)
(0)
(4)(8)
(12)
In10 ps
Out
τ
B = 87 GHz
Fractional loss≈ 1.1 dB/bit
Storage efficiency0.66 bit/RR
Pulse Broadening (1 byte)≈ 20%
ORES School, Levico, 2013 A. Melloni
ORES School, Levico, 2013 A. Melloni systems
GenericFoundries
Final Users
High level circuit designHigh level circuit design
Final User: PICs design at a circuit level using a selected set of elementary functional elements (BBs), according
to well defined rules (DKs)
materials
technol.
waveguides
devices
circuits
packaging
modules
BuilidingBlocks
Design kits
ORES School, Levico, 2013 A. Melloni
3,46
3,47
3,48
3,49
3,5
3,51
3,52
3,53
1 2 3 4
grou
p in
dex
width [um]
TE
TM
fundamental mode
Higher order mode
TE
TM
Simulation
exp
Characterization
ModellingModelling of photonic Building Blocksof photonic Building Blocks
EM analysis
Numerical simulations
E jBH jD J
B HD
S
BB model
• realistic model • no information on geometry & materials • access only to input/output port waves
• very fast, suitable for large circuits
Circuit approach(high abstraction level)
ORES School, Levico, 2013 A. Melloni
BBs of the SAPPHIRE platformBBs of the SAPPHIRE platform
Straight & bent waveguides
Directional couplers
Waveguide crossing
Bragg gratingsIn/Out mode adapter
Ring resonators
Grating assisted coupler (GAC)
Heaters
BBs of the SAPPHIRE platformBBs of the SAPPHIRE platform
Straight & bent waveguides
Directional couplers
Waveguide crossing
Bragg gratings
In/Out mode adapter
Ring resonators
Grating assisted coupler (GAC)
Heaters
ORES School, Levico, 2013 A. Melloni
ORES School, Levico, 2013 A. Melloni
Design kitsDesign kits
Lc
K
tB
tX
,BB model
Analytical model(S matrix)
Circuit parameters & variables
Mask layout
SAPPHIRE design manual
Release 1 (July 2012)
Design rules‐ BB connections
‐ validity range of the model‐ layout constraints‐ quality assessment
‐ …
ORES School, Levico, 2013 A. Melloni
Libraries for ASPICLibraries for ASPICTMTM simulatorsimulator
1600 BBs; 100 lambda points 1 min
www.aspicdesign.com
Direct exportation of the mask layout
Play with realistic BB
SAPPHIRE BBs
Phoenix
ORES School, Levico, 2013 A. Melloni
ww
w.a
spic
desi
gn.c
om
CITCUIT SIMULATOR
ww
w.p
hoen
ixbv
.com
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