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

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

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

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

Scalable Assembly: 367 Demo

DM Stroke: Position vs. Voltage Nonlinear position Very repeatable

2 nd Generation Assembled Mirrors

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

Surface Figure vs. Temperature

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

Bimorph-Flexure Temperature Stability

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 V

Detailed Position vs. Voltage Data

Experimental Deflection 3.5 micron stroke segment, 60 volts

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

Experimental Deflection - 7 segments