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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. MICROMACHINING AND MICROFABRICATION TECHNOLOGY FOR ADAPTIVE OPTICS Olav Solgaard.
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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 MICROMACHINING AND MICROFABRICATION TECHNOLOGY FOR ADAPTIVE OPTICS Olav Solgaard
mMIRRORS Texas Instrument’s DMD NASA's Next Generation Space Telescope (2008) with 4M micromirrors by Sandia NL Lucent’s Optical X-Connect
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
System on a chip Laser-to-fiber coupling Micropositioners of mirrors and gratings 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 • actuation, mirror quality, integration • Conclusion
Micromirror Structure Support Frame Mirror Surface Frame Hinge Electrostatic Combdrive Torsion Hinges Substrate Hinge Combdrive Linkage
Fabrication PolySi Nitride Oxide Slider Hinge V-groove for alignment Mirror
2.00% 1.50% 1.00% Change in Res. Frequency 0.50% 0.00% -0.50% 1.E+04 1.E+06 1.E+08 1.E+10 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 #
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
MUMPS Poly2 Static deformation 1.2 mm Mirror Curvature Measurement • 2-D Interferometry • Optical far-field measurements
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]
a b d c g h e f Video Display Scanned ImagesResolution: 62 by 66 pixels, optical scanning angles 5.3 and 5.7 degrees
Fiber Optic Crossbar Switch Input Ports l1OXC Torsion bar Mirror l2OXC 1 Frame l3 2 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
0 -20 -40 Output A Output B -60 M1: 0V to 21.7V M3: 25.5V M3: 0Vto 25.5V M1: 0V M1 M1 M2 M2 B B M4 M4 A A M3 M3 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
Optical Coherence Tomography Delay line m 760 m Beam Splitter 5.3 cm Grating Scanning Mirror
Polysilicon Grating Light Modulator ribbons 3um ribbons 6um grating period 200 um 150um electrode anchor
GLM Operation Beams up, reflection Beams down, diffraction Cross section Side view
Combdrive vs. parallel plate End view d d h Acd=4Ndh
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??
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??