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High-Performance MEMS-Based Deformable Mirrors for Adaptive Optics Iris AO, Inc.

High-Performance MEMS-Based Deformable Mirrors for Adaptive Optics Iris AO, Inc. Iris AO Inc . Founded in 2002 Small high-technology firm specializing in AO Aim to build high-performance, robust MEMS based DMs that address a large application space

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High-Performance MEMS-Based Deformable Mirrors for Adaptive Optics Iris AO, Inc.

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  1. High-Performance MEMS-Based Deformable Mirrors for Adaptive Optics Iris AO, Inc.

  2. Iris AO Inc • Founded in 2002 • Small high-technology firm specializing in AO • Aim to build high-performance, robust MEMS based DMs that address a large application space • Funded by SBIR grants, CfAO grants, consulting and driver / DM sales

  3. Iris AO Segmented MEMS DM • Robust assembled mirror surface stays flat • Temperature insensitive bimorphs elevate mirror above substrate • Piston/tip/tilt electrostatic actuation

  4. Electrostatic DM Actuators • Actuators wired to periphery • Electrostatic forces pull actuators down • No hysteresis • 4.2 mm aperture • Engineered stresses create beam shape • Stroke determined by design, not process

  5. Assembled SOI Mirrors: Benefits • Single crystal mirror has excellent flatness • Thickness gives rigidity • Mirror is still flat after optical coating • Stays flat over varying operating conditions • Temperature • Actuation • High fill factor • Mirrors cover bimorph flexures • Etch holes not necessary

  6. Scalable Assembly: 367 Demo

  7. DM Stroke: Position vs. Voltage • Nonlinear position • Very repeatable

  8. 2nd Generation Assembled Mirrors

  9. 2nd Generation Assembled Mirrors

  10. Surface Figure vs. Temperature • Optical coating on the DMs forms a bimorph that deforms with change in temperature • Some coating stacks have shown to reduce stress mismatches • These stacks do NOT help when materials plastically deform • Best coating for MEMS used for MIR is Au • Au plastically deforms at >~100MPa

  11. Surface Figure vs. Temperature

  12. Bimorph-Flexure Benefits • Stroke (gap) dictated by design, not process • Simple design with a lot of latitude for design changes • Materials chosen to minimize deflection vs. temperature • Position vs. Temperature = ~2nm/°C • Film non-uniformity across 6” wafer < ~5% • Non-uniformity across chip < 1% • Differences in height due to temperature swings are minimal

  13. Bimorph-Flexure Temperature Stability

  14. Electrostatic Actuation • No hysteresis • Nonlinear with Voltage • Highly repeatable • Temperature independent • Often high-voltages involved (200V) • High voltage is a potential reliability problem • Electrode erosion • Dielectric breakdown • Leakage currents • Dielectric charging • Iris AO DMs operate over 60-130V

  15. Detailed Position vs. Voltage Data

  16. Experimental Deflection 3.5 micron stroke segment, 60 volts

  17. Experimental Deflection - High Stroke 7.5 micron stroke segment, 130 volts

  18. Experimental Deflection - 7 segments

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