Design and Fabrication of Deformable Polymer Micromirror for Adaptive Optic Systems

This paper presents a novel method for the fabrication of polymeric deformable micromirror based on electrostatic actuator. Deformable micromirros are commonly used to correct optical wavefront aberrations in the adaptive optic systems, and thus, they need a deformable diaphragm. In this study, the diaphragm of micromirror is made from SU-8 polymer which is mounted on the fixed electrode arrays. This polymeric diaphragm with a Young’s modulus of 50 times less than conventional silicon samples provides more deformability and, as a result, aberrations modifications with lower voltage values are reached, so that the diaphragm with a radius of 2.5 mm and a thickness of 10 μm moves about 4μm by applying the voltage of 120 volts. Furthermore, polymer-based fabrication processes are more simple and cost-effective rather than silicon-based devices. However, they suffer from lower surface roughness compared to silicon-based counterparts. In order to overcome this issue, we used a new technique for the manufacture of micromirror, which, in addition to all the advantages of a polymeric mirror, provides similar surface smoothness of the silicon samples. The result of roughness measurements showed a rough surface variance of 20 nm. The Finite Element Modeling is also used to optimize the device structure design.