Foundry microfabrication of deformable mirrors for adaptive optics

Microelectromechanical Systems (or MEMS) is a rapidly emerging field of research in which batch fabrication processes, similar to those of the integrated circuit industry, are used to construct miniature devices with moving parts. MEMS devices are particularly well suited to optical applications, where microscopic deflections can produce macroscopic results. Although existing MEMS foundry processes have not been optimized for optical applications, the use of foundry microfabrication offers a substantial cost advantage for prototype system development through low volume production. In this dissertation research effort, foundry MEMS processes are used to fabricate low-cost deformable mirror systems (MEM-DMs) for adaptive optics. The challenges and design trades associated with fabrication of continuous and segmented deformable mirrors in foundry processes are examined in detail. The importance of controlling micromirror surface figure is experimentally demonstrated, and post-foundry metallization techniques are shown to improve the optical performance of foundry fabricated piston micromirror arrays. Beam steering and optical aberration correction experiments, with and without using a lenslet array to improve optical characteristics, conclusively demonstrate the potential of low-cost MEM-DMs. The prototype MEM-DM systems are approximately 1/500{dollar}rmsp{lcub}th{rcub}{dollar} the cost of conventionally manufactured deformable mirrors. Optical experiment results show good agreement with theory. The development of an innovative direct digital control scheme further reduces adaptive optic system cost by eliminating the digital to analog converter typically required for each controlled element. In addition to the MEM-DMs demonstrated, other MEMS devices are shown. Two dimensional arrays of thermally actuated piston micromirrors are designed and tested. The thermally actuated devices offer greater deflections for operation at longer optical wavelengths. A variety of tilting and beam steering mirrors are demonstrated, including two-axes steering mirrors which are self-assembled using metal stress cantilevers. Other MEMS devices examined include pressure gauges, test structures, electrostatic scratch drive actuated rotors, and a new type of electrostatic cantilever motor with lateral motion output.