Design and fabrication of 10 X 10 micro-spatial light modulator array for phase and amplitude modulation

In this paper, a 10 x 10 micro-spatial light modulator (micro-SLM) array fo r phase and amplitude modulation of incident light is designed and fabricat ed using surface micromachining technology. Hidden spring structure is used in order to maximize the fill-factor and minimize diffraction effect. A de signed micro-SLM is composed of a mirror plate, upper electrodes, five supp ort posts, and bottom electrodes. The spring structures are composed of fou r double crab leg springs for phase modulation (piston mode operation) and two torsional springs for amplitude modulation (tilt mode operation). The m icro-SLM is actuated by electrostatic force generated between upper electro de and bottom electrode. In case of phase modulation, the maximum deflectio n length of mirror plate is designed to be 4 mu m and in case of amplitude modulation, micro-SLM is designed to be capable of tilting +/-5.4 degrees t o reflect incident light. The designed micro-SLM array is successfully fabr icated with surface micromachining technology using thick photoresist as a sacrificial layer and aluminum as a structural material. Mirror plate and s pring structure are fabricated without initial bending problem. The resulti ng fill-factor is about 91.7%. Static and dynamic characteristics of the fa bricated micro-SLM in the case of amplitude modulation are measured with op tical measurement system. In the fields of adaptive optics and pattern reco gnition system, SLM is used to modulate the phase and amplitude of incident light in order to correct aberration in an optical system through active c ontrol of mirror array. (C) 1999 Elsevier Science S.A. All rights reserved.