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MEMS Deformable Mirrors in Astronomical AO

MEMS Deformable Mirrors in Astronomical AO. Thomas Bifano Director, Boston University Photonics Center (BUPC) Chief Technical Officer, Boston Micromachines Corporation (BMC) Paul Bierden President, BMC Steven Cornelissen, VP, BMC AO4ELT, Paris, 25 June 2009.

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MEMS Deformable Mirrors in Astronomical AO

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  1. MEMS Deformable Mirrors in Astronomical AO Thomas Bifano Director, Boston University Photonics Center (BUPC) Chief Technical Officer, Boston Micromachines Corporation (BMC) Paul Bierden President, BMC Steven Cornelissen, VP, BMC AO4ELT, Paris, 25 June 2009

  2. Microelectromechanical (MEMS) DMs Over the past decade, we’ve led an academic program at the Boston University Photonics Center (BU), and a technology development program at Boston Micromachines Corporation (BMC), to pioneer and demonstrate DMs made with semiconductor foundry processes. Attachment post Electrostatic actuator array Mirror + Silicon wafer

  3. Two DMs described in this talk 4096 actuator continuous membrane DM for Gemini Planet Imager 331 segment (993 actuator) hexagonal tip-tilt-piston DM for NASA TPF-C visible nulling coronagraph

  4. Application: Gemini Planet Imaging (4K DM) Gemini Planet Imager: 4096 actuator DM (BMC), with 3.5µm stroke, for Jovian exoplanet detection. Engineering mirror delivered, science mirror due. B. Macintosh, J. Graham, D. Palmer et al., “Adaptive optics for direct detection of extrasolar planets: the Gemini Planet Imager,” Comptes Rendus Physique, vol. 8, no. 3-4, pp. 365-373, Apr-May, 2007.

  5. Some DM Requirements for 4K GPI DM

  6. 4K DM Prototype Results >4µm stroke achieved @ 210V 2.6mm 4.32µm High spatial frequency print-through reduced to <10nm RMS 1.15µm Interactuator stroke achieved Previous DM: 21.5nm RMS Phase I DM: 5nm RMS 175nm 80nm 1150nm 1000µm 200µm 0nm 0nm 0nm

  7. Measured Optical Quality Measured surface Filtered surface (uncontrollable) 6µm 200nm 0µm 0nm 4.06µm PV 707nm RMS 48m ROC 40nm PV 4nm RMS 16RW013#001 Top right zone (showing scallop at periphery) Center zone 50nm 100nm 0nm 0nm ~50nm PV ~25nm PV

  8. DM Static Cold Test @ 24.7C @ -20.2C

  9. Cycling & Hysteresis

  10. Package and Driver

  11. This MEMS DM architecture permits ultraprecise, repeatable control 144nm Initial 12nm Controlled J. W. Evans et al., Optics Express 14, 5558 (2006) • 1024 actuator MEMS DM • Controllable flatness <12nm • Actuator repeatability <1nm • Hysteresis <1nm Three research groups have developed precise models of MEMS DM behavior, including mechanical coupling through the mirror and nonlinear actuation electromechanics. Result: We can now achieve open-loop shape control within 25nm error in one step. J. B. Stewart, A. Diouf, Y. P. Zhou, T. G. Bifano, Journal of the Optical Society of America 24, 3827 (Dec, 2007).

  12. 331 Element Tip-Tilt-Piston MEMS DM +/-6mrad tip-tilt 2um piston 600µm

  13. Hex Mirror Segments Use thick, eptiaxial-grown polysilicon layer (6-10µm) to achieve surface figure requirement 5.9 nm ± 0.2nm RMS over DM aperture 35nm 0nm Actual Segment Thickness: 7.5µm

  14. Acknowledgements MEMS DM Students: Y. Zhou, J. Stewart*, J. Perreault, R. K. Mali, Andrew LeGendre BMC Technical Research Staff: A. Hartzell, P. Bierden, S. Cornelissen, J. Stewart, P. Woskov, C. Lam Funding: CfAO, Gemini, NASA, DARPA

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