1. 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

2. mMIRRORS Texas Instrument’s DMD
NASA's Next Generation Space Telescope (2008) with 4M micromirrors by Sandia NL
Lucent’s Optical X-Connect

3. 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

4. System on a chip Laser-to-fiber coupling Micropositioners of mirrors
and gratings
High-resolution raster scanner

5. 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

6. Micromirror Structure
Support Frame
Mirror Surface
Frame Hinge
Electrostatic Combdrive
Torsion Hinges
Substrate Hinge
Combdrive Linkage

7. Fabrication PolySi Nitride Oxide Slider Hinge V-groove for alignment
Mirror

8. Micromirror Reliability
-0.50%
0.00%
0.50%
1.00%
1.50%
2.00%
1.E+04
1.E+06
1.E+08
1.E+10
Change in Res. Frequency
Micromirror Reliability
x 10
“Off” position -3 1
0.5
Angle (degrees)
-0.5 -1 10 20 30 40 50 60 70 80
measurement #

9. 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

10. Mirror Curvature Measurement
Static deformation 1.2 mm
MUMPS Poly2
2-D Interferometry
Optical far-field measurements

11. 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
Degrees
600
500
-.001
400
-.002 -2 -1 1 2
300
Degrees -4 -3 -2 -1 1 2 3 4
Mechanical deflection [deg]

12. a d e c f b g h
Scanned Images Resolution: 62 by 66 pixels, optical scanning angles 5.3 and 5.7 degrees
Video Display

13. Fiber Optic Crossbar Switch
Input
Ports
l1OXC
Torsion
bar
Mirror
l2OXC 1
Frame 2 l3
Output
Ports
Comb
drive 3
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

14. Demonstration of Crossbar Switch
M1: 0V to 21.7V
M3: 25.5V
M3: 0Vto 25.5V
M1: 0V M1 M3 M2 M4 B A
-60
-40
-20
Output A
Output B
Input Mirror
Array
Optical Power Transmision [dB]
Output Mirror
Array
2X2 OXC design
Switch characteristics Horizontal axis is in volts squared

15. Optical Coherence Tomography
Delay line
760 m m
Beam
Splitter
5.3 cm
Grating
Scanning Mirror

16. Polysilicon Grating Light Modulator
ribbons
3um ribbons
6um grating period
200 um
150um
electrode
anchor

17. GLM Operation Cross section Side view Beams up, reflection
Beams down, diffraction
Cross section
Side view

18. Combdrive vs. parallel plate
End view d h
Acd=4Ndh

19. 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
Novel functions - Diffractive optics
Spectral filtering??

20. 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??