A continuous-membrane micro deformable mirror based on anodic bonding of SOI to glass wafer

As one of the most important components in adaptive optics, the deformable mirror (DM) is required to have a flat surface for better performance. For micromachined DMs, single-crystal-silicon (SCS) membrane is an ideal material for high quality reflective mirror surface owing to its good flatness and small residual stress. In this research, a process was established to realize SCS mirror membrane by DRIE of SOI wafer and anodic bonding of SOI wafer to Pyrex 7740 glass. Using this process, the proof-of-concept for a micromachined DM composed of SCS mirror surface has been successfully demonstrated. The prototype DM shows a stroke of 4.23 μm at 120 V. The P-V and rms of the reflective mirror surface are 492 and 82 nm, respectively. The performance of the prototype DM can somewhat satisfy the need of AO in visible spectrum. Better surface quality is anticipated by employing SOI wafers with strictly controlled residual stress.