Optical characterization of MEMS deformable mirror array structures

Abstract

Surface properties and optical properties of several deformable mirror arrays (DMA) without actuators were characterized. The mirror arrays are micro-electronic- mechanical system (MEMS) devices which were fabricated by Boston University for wavefront correction in adaptive optics. The surface properties measured for the samples agree with the properties specified for the BU-MEMS-DMA structures. Scattering and diffraction by the mirror arrays were measured at a wavelength of 632.8nm. The DMA with the etching pattern generates a diffraction pattern full of special structures. The broadening is serious for a rough sample while it is negligible for a smooth continuous membrane DMA. The diffraction pattern demonstrates that the DMA with an RMS roughness of 300nm is not suitable for the adaptive optics to correct for wavefront error. The continuous membrane DMA with roughness less than 10 nm are useful for adaptive optics.