Micromachined deformable mirrors for dynamic wavefront control

High-Contrast Imaging using Adaptive Optics for Extrasolar Planet Detection

“…The interferometry mode is used for optical metrology and closed-loop operations. A 1024-actuator MEMS DM [50] was installed and closed-loop performance was characterized with the PSDI as the wavefront sensor (WFS) [60]. The precision wavefront correction of < 1 nm over controllable spatial frequencies should yield excellent contrast.…”

“…The MEMS devices tested with the voltage limits used have particularly limited stroke (about 1 µm). However, the more limited stroke of these particular devices is not a concern because other device geometries with larger actuator spacing have demonstrated 4 µm of stroke [50]. Those geometries will be used for the future 4000-actuator device needed for GPI.…”

“…We have tested a total of ten 1024-actuator deformable MEMS mirrors fabricated by BMC [50]. While a future exoplanet imager will require more actuators, the 69 1024 device is the largest commercially available MEMS device.…”

“…Initial high-contrast measurements focused on measurement techniques and instrumentation without active correction, in particular, suppressing diffraction, understanding the high-contrast regime and developing experimental methods for high-contrast imaging (i.e., controlling scattered light) [26]. After initial tests, a 1024-actuator MEMS deformable mirror, developed by Boston Micromachines Corporation (BMC) [50], was installed for active wavefront control. [26].…”

“…Batch processing techniques, such as those pioneered in the integrated circuit industry, are used to produce many DMs at once, greatly reducing the cost. Typically these devices are made with lithographic techniques, which layer polysilicon with sacrificial phosphosilicate [50] glass layers to produce individually addressable actuators made of polysilicon using the mulit-user MEMS process (MUMPS)…”