Download solgaard - Center for Adaptive Optics

MICROMACHINING AND
MICROFABRICATION TECHNOLOGY
FOR ADAPTIVE OPTICS
Olav Solgaard
Acknowledgements:
P.M. Hagelin, K. Cornett, K. Li,
U. Krishnamoorthy, D.R. Pedersen,
M. H. Guddal, E.J. Carr, V. Laible,
Research Funding:
NSF, BSAC, SMART
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BSAC: R.S. Muller, K. Lau, R.
Conant, M. Hart
mMIRRORS
Texas Instrument’s DMD
NASA's Next Generation Space
Telescope (2008) with 4M
micromirrors by Sandia NL
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Lucent’s Optical X-Connect
mGRATINGS - DIFFRACTIVE OPTICS
Top electrode
Silicon Nitride
Silicon Substrate
Silicon Dioxide
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 1-D and 2-D spatial
light modulators
(Projection displays Silicon Light Machines)
 Displacement sensors
(AFM arrays - C. Quate)
 Sensor integration,
free-space
communication
 Diffractive lenses and
holograms (Fresnel
zone plates - M. Wu,
UCLA)
System on a
chip
Laser-to-fiber coupling
Micropositioners of mirrors
and gratings
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High-resolution raster scanner
Why Micromachined Adaptive Optics?
 Parallel processing, large arrays, system
integration, diffractive optics
• Standard IC materials and fabrication
• Integration of optics, mechanics, & electronics
 Scaling of optics
• Alignment, Resolution, Optical quality,
Mechanical actuation and stability
• Raster-scanning displays, Fiber-optic switches,
Femto-second spectroscopy
 Technology development
 Conclusion
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• actuation, mirror quality, integration
Micromirror Structure
Support Frame
Electrostatic
Combdrive
Combdrive
Linkage
Frame
Hinge
Torsion Hinges
Substrate
Hinge
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Mirror Surface
Fabrication
PolySi
Nitride
Oxide
Hinge
Mirror
V-groove for
alignment
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Slider
Change in Res. Frequency
1.50%
1.00%
0.50%
0.00%
-0.50%
1.E+04
1.E+06
1.E+08
1.E+10
“Off” position
x 10
-3
1
0.5
0
-0.5
-1
0
10
20
30
40
50
measurement #
60
70
80
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Angle (degrees)
Micromirror
Reliability
2.00%
Video Display System Schematic
• Demonstration system used two mirrors on separate chips
Computer modulates a 10
mW 655 nm laser diode
The emerging beam hits
the fast scanning mirror
1f
2f
1f
The beam is then imaged
to the slow scanning
mirror
…and the image is
projected onto a
screen
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The light is
coupled into a
single-mode fiber
Mirror Curvature Measurement
MUMPS Poly2
 2-D Interferometry
 Optical far-field
measurements
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Static deformation 1.2 mm
Mirror curvature due to actuation
Mirror deformation due to actuation
Wobble of actuated
micromirror (motion on
orthogonal axis)
1100
900
.002
800
.001
700
Degrees
600
0
500
-.001
400
-.002
-2
300
-4
-3
-2
-1
0
1
2
3
4
-1
0
1
2
Degrees
Mechanical deflection [deg]
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Optical beam radius (1/e2 ) [mm]
1000
Scanned
Images
a
Resolution: 62 by
66 pixels, optical
scanning angles
5.3 and 5.7
degrees
b
e
d
c
g
f
h
50
50
100
100
Video
Display
150
200
200
250
250
300
300
350
350
400
400
450
450
100
200
300
400
100
500
200
600
300
400
500
600
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150
Fiber Optic Crossbar Switch
l1OXC
l2OXC
l3
1
2
3
Output
Ports
Optical
DMUX
1
2
3
Optical
MUX
Architecture of WDM Switch
The optical input signals are demultiplexed,
and each wavelength is routed to an
independent NxN spatial cross-connect
Torsion
bar
Comb
drive
Mirror
Frame
500 mm
SEM of the micromirrors
used in the two-chip switch
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Input
Ports
Input Mirror
Array
Optical Power Transmision [dB]
Demonstration of Crossbar Switch
0
-20
-40
Output Mirror
Array
Output A
Output B
-60
M1: 0V to 21.7V
M3: 25.5V
M3: 0Vto 25.5V
M1: 0V
2X2 OXC design
M1
M1
M2
Horizontal axis is in volts squared
B
M4
B
M4
M3
A
A
M3
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Switch characteristics
M2
Optical Coherence Tomography
Delay
line
760 mm
Grating
5.3 cm
Scanning Mirror
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Beam
Splitter
Polysilicon Grating Light Modulator
ribbons
3um ribbons
6um grating period
200 um
electrode
anchor
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150um
GLM Operation
Beams up, reflection
Cross section
Side view
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Beams down, diffraction
Combdrive vs. parallel plate
N 0 hV 2
Combdrive : Fcd 
d
Parallel plate : F pp 
Acd  4 Ndh  Fcd 
A pp 0V 2
2s 2
Acd  0V 2
4d 2
End view
d
d
h
Acd=4Ndh
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2
Fcd
s

F pp 2d 2
Lessons for Adaptive Optics
 Standard processes and materials
• High-resolution optics
• Mechanical stability & reliability =>
electrostatic actuation
• Large-stroke actuation => Combdrives
 Optical quality
• SOI material
 Integration
• wafer bonding => optimization of optics,
mechanics and electronics
• Spectral filtering??
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 Novel functions - Diffractive optics
Conclusion
 Micromachining enables Adaptive Optics
• Miniaturization, arrays, integration, parallel
processing, robustness, reliability
• Standard materials and processing  Low cost
 Technology development
• Large-stroke electrostatic actuators
• High-quality optics
• Integration
Wafer bonding
Through-the-wafer interconnects
• Diffractive optics??
• Spectral filtering??
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 Novel functions