MICROMACHINING%20AND%20MICROFABRICATION%20TECHNOLOGY%20FOR%20ADAPTIVE%20OPTICS

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• 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, BSAC R.S.
Muller, K. Lau, R. Conant, M. Hart Research
Funding NSF, BSAC, SMART
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mMIRRORS
Texas Instruments DMD
NASA's Next Generation Space Telescope (2008)
with 4M micromirrors by Sandia NL
Lucents Optical X-Connect
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mGRATINGS - DIFFRACTIVE OPTICS
Top electrode

• 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)

Silicon Nitride
25 to 100 µm
Silicon Substrate
Silicon Dioxide
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System on a chip
Laser-to-fiber coupling
Micropositioners of mirrors and gratings
High-resolution raster scanner
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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
• actuation, mirror quality, integration
• Conclusion

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Micromirror Structure
Support Frame
Mirror Surface
Frame Hinge
Electrostatic Combdrive
Torsion Hinges
Substrate Hinge
Combdrive Linkage
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Fabrication
PolySi
Nitride
Oxide
Slider
Hinge
V-groove for alignment
Mirror
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MicromirrorReliability
x 10
Off position
-3
1
0.5
Angle (degrees)
0
-0.5
-1
0
10
20
30
40
50
60
70
80
measurement
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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
The light is coupled into a single-mode fiber
and the image is projected onto a screen
2f
1f
The beam is then imaged to the slow scanning
mirror
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Mirror Curvature Measurement

• 2-D Interferometry
• Optical far-field measurements

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Mirror curvature due to actuation
Mirror deformation due to actuation
Wobble of actuated micromirror (motion on
orthogonal axis)
1100
1000
) mm
900
.002
2
800
.001
700
Optical beam radius (1/e
0
Degrees
600
-.001
500
400
-.002
-2
-1
0
1
2
300
Degrees
-4
-3
-2
-1
0
1
2
3
4
Mechanical deflection deg
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Video Display
Scanned Images Resolution 62 by 66 pixels,
optical scanning angles 5.3 and 5.7 degrees
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Fiber Optic Crossbar Switch
Input Ports
l1OXC
Torsion bar
Mirror
l2OXC
1
Frame
l3
2
Output Ports
Comb drive
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Optical DMUX
1
2
3
500 mm
Optical MUX
Architecture of WDM Switch The optical input
signals are demultiplexed, and each wavelength is
routed to an independent NxN spatial
cross-connect
SEM of the micromirrors used in the two-chip
switch
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Demonstration of Crossbar Switch
Input Mirror Array
Optical Power Transmision dB
Output Mirror Array
2X2 OXC design
Switch characteristics Horizontal axis is in
volts squared
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Optical Coherence Tomography
Delay line
m
760
m
Beam Splitter
5.3 cm
Scanning Mirror
Grating
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Polysilicon Grating Light Modulator
ribbons
3um ribbons 6um grating period
200 um
150um
electrode
anchor
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GLM Operation
Beams up, reflection
Beams down, diffraction
Side view
Cross section
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Combdrive vs. parallel plate
End view
d d
h
Acd4Ndh
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Lessons for Adaptive Optics

• Standard processes and materials
• High-resolution optics
• Mechanical stability reliability gt
  electrostatic actuation
• Large-stroke actuation gt Combdrives
• Optical quality
• SOI material
• Integration
• wafer bonding gt optimization of optics,
  mechanics and electronics
• Novel functions - Diffractive optics
• Spectral filtering??

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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
• Novel functions
• Diffractive optics??
• Spectral filtering??