Membrane Deformable Mirror for High Contrast Astronomical Imaging

Presented in this paper is the development of a 4096 element continuous membrane deformable mirror under development for the Gemini Planet Imaging instrument designed for extra solar planet detection. This deformable mirror will enable the next generation of adaptive optics (“Extreme ” AO) capable of achieving contrasts of up to 108, required to detect these planets that are obscured by the brightness of its parent star. This surface micromachined MEMS deformable mirror will have an active aperture of 25.2mm consisting of thin silicon membrane mirror supported by an array of 64x64 electrostatic actuators exhibiting no hysteresis and sub-nanometer repeatability. This deformable mirror will be capable of 4µm of stroke, have a surface finish of <10nm RMS with a fill factor of 99.8%, and be capable of frame rates in excess of 2.5kHz. This development effort combines new design features, fabrication processes and packaging methods with those developed for commercially available 1024 and 140 element MEMS deformable mirrors to achieve unprecedented performance and reliability. Keywords: Deformable mirror, MEMS, adaptive optic