<title>Design and fabrication of hidden-spring-structure-type micro-SLM for phase and amplitude modulation</title>

Abstract

In the fields of adaptive optics and pattern recognition system, SLM is used to modulate the phase and amplitude of incident light in order to correct aberration in an optical system through active control of mirror array. In this paper, a micro spatial light modulator (SLM) array, which has one hundred of micro SLM, that is to say, 10 X 10 array, for phase and amplitude modulation of incident light is designed and fabricated using surface micromachining technology. In order to maximize the fill factor and minimize diffraction effect, hidden spring structure is used. A designed micro SLM is composed of a mirror plate, upper electrode, five support posts, and bottom electrode. The spring structures are composed of double crab leg spring for phase modulation and torsional spring for amplitude modulation. The micro SLM is actuated by electrostatic force generated by electric potential applied between upper electrode and bottom electrode. In case of phase modulation, the maximum deflection length of mirror plate is 4 micrometers and in case of amplitude modulation, it is designed to be capable of tilting +/- 5.4 degree(s) to reflect incident light.