Segmented MEMS deformable-mirror technology for space applications

摘要

This paper presents MEMS deformable-mirror technology under development at Iris AO. The hybrid approach uses surface-micromachining techniques to fabricate actuator arrays. High-fill-factor mirror arrays are flip-chip bonded on top of these actuator arrays. The single-crystal-silicon mirror segments provide robust substrates for optical coating with excellent surface quality (6-20 nm rms surface-figure errors). The hexagonally close-packed segments are 350 μm on a side, and can thus provide high-spatial frequency corrections in a small form factor. High-stroke actuation of greater than > 7.5 μm has been experimentally verified while keeping actuation voltages within reasonable bounds (< 130 V). Three electrodes under each actuator allow for piston/tip/tilt motion. An open-loop controller has been demonstrated to position a 37-segment array resulting in a flattened array with only 19 nm rms of surface figure error.