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Introduction to NanoScan
2
Introduction to NanoScan
• How does it work?
• What is a slit profiler good for?
• How does it differ from a CCD?
• Who wants one?
• Why do they want it?
• How do you sell it and to whom?
3
NanoScan
How does it work?
4
Beam Sampling Technique
5
Beam Sampling Technique
6
Slit Scanner Operation
7
What is it good for?
• In general, NanoScan
is used for focused or
collimated beams
8
Beam Width, Clip Level Method
Irra
dia
nce
Distance Across Beam
100%
13.5% (1/e2)
Irradiance = Power/unit area
FWHM
Laser Beam Profile
Centroid
9
4-Sigma Measurement
4-sigma measurement points
10
NanoScan d4 2nd Moment Calculation
Slit Scanner Output Profile
Profile for narrow slit
2nd Moment from slit profile
Discrete sum in practice
11
Ellipticity
DX
DY
E = DX
DY
12
NanoScan Configurations
• Silicon Detector
– 190-900nm
• Germanium Detector
– 700-1800nm
• Pyroelectric detector
– 200nm->>20μm
Measures most Wavelengths
13
Available NanoScan Scan Heads
• Silicon Detector (visible λ)
– λ =190 to 900 nm
• Not recommended for >1000nm
– 10 μm to 20 mm spot size range
• Germanium Detector (near IR λ)
– λ =700 to 1800 nm
– 10 μm to 12 mm spot size range
• Pyroelectric Detector
– λ =0.25 to 20 μm including 10.6 μm
– 20 μm to 20 mm spot size range
NanoScan Configurations
14
NanoScan Configurations
• Standard Head has 2 Apertures—3.5mm, 9mm
– 3.5 mm Aperture has 1.8μm Slit Size
– 9 mm Aperture has 2 Slits
• 5μm and 25μm
• Large Aperture Heads
– 25mm for Si, 20mm for Pyro, 12mm for Ge
– Slits 25μm
Measures very small beams
15
How small a beam can be measured?
• Selection of slit width:
– 1/4 or less than 1/e2 beam width
• Selection of aperture size; e.g.
– 3.5mm –1.8µm slit
– 9mm—5µm or 25µm slits
16
Convolution Error
• Due to the Convolution Effect, slit width
should be smaller than 25% of the 1/e2 width
of beam.
17
NanoScan Operating Space Advantage
Has very large dynamic range
18
Advantages of Dynamic Range
• Measures focus and defocused beam
• Measures most beams without attenuation
• No need for adjustments to beam or
attenuation during measurements
• Excellent for M2 Measurements
– Makes NanoModeScan fast
19
Slit Plane is
Measurement Plane
Measures Beam Directly
20
Slit Plane Well-defined
21
Advantages of Known Slit Plane
• Measures tightly focused Beams
• Finds beam waist locations to high precision
• Reproducible measurements
• Guarantees optical system performance
22
Pointing Accuracy
• Very low jitter
• Pointing precision to ~50nm
• Guarantees consistent performance
• Accurate pointing measurement in small space
23
Other Capabilities-Multiple Beam Analysis
• Up to 16 Beams
• Measures individual
parameters
• Linear arrays only
• Operate at 45°Use
Rotation
transformation in
software
– Analysis window
– Enter 45°
24
Rotational transformation
• Changes the coordinates
from default
• Report separation as
linear
• Operation at 45°
precludes elliptical
analysis
• Beams will be assumed to
be round
• Use for alignment, not
detailed structure analysis
25
ROI Selection
• Up to 16 ROIs
• Color coded for display
of individual beam data
• Automatic or manual
selection
– Drag and drop
– Numerical input to dialog
box
26
What Doesn’t it Do?
27
2-D/3-D Image is only an approximation
28
Real 2D/3D is for Cameras
Customers who want a
real 2-D image of their
beam should get a
camera.
NanoScan is for
measuring beam width of
generally Gaussian or
semi Gaussian beams
NanoScan is not good for
higher order beam types
NanoScan does not
measure flat-top beams
well
29
Slow Pulsed Beams
• NanoScan measures beams >5kHz rep rate
• Use Cameras for slower repetition rates.
30
Measuring Pulsed Beams with the
NanoScan Slit Profiler
31
What Sort of Pulsed Beams can be measured?
• Must be 5kHz and above repetition rate
• Must be stable
– Rep Rate
– Power per pulse
• Energy per pulse must not exceed Damage
thresholds
• Average power must be in operating space
32
Types of Pulsed Beams
• Pulse Width Modulated (PWM)Lasers
– Power control
– Common in CO2 Lasers
• Q-Switched Lasers
– Method of increasing effective power
– Short pulses
• Pico- and Femtosecond Lasers
– Lower average power
– Very high peak powers
– Energy per Pulse (Epulse) important parameter
33
Pulsed Beams
• CO2 Pulse Width
Modulation @ 50%
• Picket Fence
• 10kHz Rep Rate
• Pulse Mode Off
34
Pulsed Beams
• PWM @ 95%
• Typical Power control
for CO2 lasers
• User often thinks it’s
CW, or
• User does not know
the rep frequency
35
Pulsed Mode On
• Peak Connect algorithm
• Finds Peaks
• Uses Repetition
Frequency to draw peak
• Must have the right
Frequency
• NanoScan measures
Frequency
36
Repetition Frequency vs Beam Size
37
38
Pulsed Beam Complications
• Pulse Width Modulation
– Treat like CW for Power calculations
– Use Average Power
• Q-Switched and other energy increasers
– For pulse durations <10-6 second (<1μsec) or
shorter
– Calculate Energy per pulse
– Use the Slit Damage Calculator
39
Problematic Pulsed Beams
• Lasers with uneven power per pulse
– Peak connect can find beam top
– Unstable profile
• Lasers with too low pulse rate for beam size
– Camera may be necessary
• Femtosecond Lasers
– Can have very high peak powers
– Non linear effects on slit material
– Not well understood at this time
40
Pulse Effects on Power
• Epulse goes down as
frequency increases
• Ppulse increases as
pulse duration
decreases
• This can be dramatic
as durations approach
10-12 (ps) or 10-15
(fs)
41
Measuring fsec and psec Lasers
• Determine the Energy per pulse
laser
avg
pulsef
PE
42
Measuring psec and fsec Lasers
• Calculate Energy Density per pulse for 100μm
Beam:
43
44
Damage Thresholds
• 5J/cm2—Cu Slits at >3μm
• 2.5J/cm2—Cu Slits 700nm-3μm
• 1J/cm2—Ni Slits at >400nm
• 600mJ/cm2—Ni Slits at 190nm-400nm
• 10mJ/cm2—Blackened slit material
45
NanoScan Heads for fsec Lasers
• Use Average Power to Select Detector
• Use Epulse to determine aperture type
• Use Unblackened Slits and Drums
• High frequency (>100kHz) lasers can be
measured in CW mode with filtering
46
Potential Issues of Short Pulses
• Changing Frequency alters Energy
• The lower the frequency, the higher the Energy
per Pulse
• Can exceed the damage thresholds
• Use the Calculator
47
Slit Damage Calculator
Slit WL Range Diameter(um)Avg Pwr(W)Freq(kHz) Pulse Width (nsec) Energy(J) Power Density(W/cm^2) Energy density (J/cm^2) Peak Irradiance (W/cm^2)Cu >3um 1000 500 5 50 1.00E-01 6.37E+04 1.27E+01 4.00E+06
Cu 700nm-3um 75 50 cw NA NA 1.13E+06 NA NA
Ni/Cu 190-400nm 20 1 10 100 1.00E-04 3.18E+05 3.18E+01 2.00E+03
Ni >400nm 80 0.5 50 0.1 1.00E-05 9.95E+03 1.99E-01 2.00E+05
Ni Blk 190-700nm 75 0.001 10 0.0001 0.0000001 2.26E+01 2.26E-03 2.00E+06
Ni Blk 700nm>3um 1000 0.1 cw na NA 1.27E+01 NA NA
6
48
Four Key Questions for Selecting a Profiler
• What wavelength is the light?
• What is the spot size? How is it defined?
• What is the beam power?
• Is the beam pulsed or continuous
wave (CW)?
49
What Wavelength is the Light?
• Determines the detector
– Silicon 190 - 1000 nm
– Germanium 700 - 1800 nm
– Pyroelectric 200nm – 20+ µm
(high power)
50
51
What is the Beam Width?
• Selection of slit width:
– 1/4 or less than 1/e2 beam width
• Selection of aperture size; e.g.
– NanoScan 3.5mm
– 9mm
– Large Aperture
• Si—25mm
• Ge—12mm
• Pyro—20mm
52
Convolution Error
• Due to the Convolution Effect, slit width
should be smaller than 25% of the 1/e2 width
of beam.
53
What is the Beam Power?
• Check the Operating Space Charts
• Make sure the beam won’t damage the
scanhead or slits
• Is the pyroelectric detector the best option?
54
Is the laser CW or pulsed?
• If CW, All OK
• Is frequency high enough?
– >1kHz
– Fast enough for the beam size
• >100kHz treat like CW
–
55
How do NanoScan Applications differ from
CCD Apps? • NanoScan gives real time feedback
– No in-test adjustments necessary
– Direct, often optics-free, measurements
• Used for Processes
– Focusing lasers
– Adjusting optics
– Collimation
– Aligning Optics
• All in Real Time
56
NanoScan Customers are
usually working on a Process
57
NanoScan Applications
• Usually simple result required
– Beam Size
– Beam Position
– Divergence
• Not looking for complex beam shapes
• Use is not unlike a power meter
– Instant feedback
– Measure while adjusting
58
NanoScan Markets & Applications
• Laser Printers
– R & D product development
– Component inspection; sub-assembly
– Final scan lens test
– LD collimators
• Bar Code Scanners
– Component sub-assembly
– LD collimators sub-assembly
• Optical Memory
– Mostly R & D
– LD collimators sub-assembly
59
NanoScan Markets & Applications
• Laser and LED manufacturers
– R & D and production
– Production test laser manufacturing paraxial
sources
• Fiber optic passive component manufacturers
– GRIN lens collimation
– Coupling LD to fiber
– Test of diffractive optic lens
– NA of fiber
60
NanoScan Markets & Applications
• Laser optical system builders
– Component test
– Sub-assembly
– Final test
– Verification in installed systems
– Assist source replacement in field
• Medical laser optical systems
– Final test
– Component test
61
Who buys NanoScan?
• Industrial Customers who want:
– Ease of use
– Speed
– Reproducible results
– Accuracy of Measurement
• Minimal optics
• Minimal variables in set up
62
Who buys NanoScan?
• Research customers who:
– Need to measure small beams
– Want to measure high power beams with minimal
attenuation.
– Have complex optical systems
– Work in IR wavelengths where NanoScan is less
expensive alternative
– Have multiple laser systems to measure
63
Who buys NanoScan?
• Laser manufactures who want:
– To match users’ measurement techniques
– Speed of measurement
– Reproducible results
64
Who buys NanoScan?
• Customers who need:
– Pointing accuracy
• Laser printer
• Military sighting and rangefinding
• Marking machines
– Collimation
– Cost-effective IR applications
– Small beam applications
65
Contact us for a demo