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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, Research Funding: NSF, BSAC, SMART os, 9/16/99 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 os, 9/16/99 Lucent’s Optical X-Connect mGRATINGS - DIFFRACTIVE OPTICS Top electrode Silicon Nitride Silicon Substrate Silicon Dioxide os, 9/16/99 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 os, 9/16/99 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 os, 9/16/99 • actuation, mirror quality, integration Micromirror Structure Support Frame Electrostatic Combdrive Combdrive Linkage Frame Hinge Torsion Hinges Substrate Hinge os, 9/16/99 Mirror Surface Fabrication PolySi Nitride Oxide Hinge Mirror V-groove for alignment os, 9/16/99 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 os, 9/16/99 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 os, 9/16/99 The light is coupled into a single-mode fiber Mirror Curvature Measurement MUMPS Poly2 2-D Interferometry Optical far-field measurements os, 9/16/99 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] os, 9/16/99 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 os, 9/16/99 150 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 os, 9/16/99 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 os, 9/16/99 Switch characteristics M2 Optical Coherence Tomography Delay line 760 mm Grating 5.3 cm Scanning Mirror os, 9/16/99 Beam Splitter Polysilicon Grating Light Modulator ribbons 3um ribbons 6um grating period 200 um electrode anchor os, 9/16/99 150um GLM Operation Beams up, reflection Cross section Side view os, 9/16/99 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 os, 9/16/99 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?? os, 9/16/99 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?? os, 9/16/99 Novel functions