Design and Analysis of The CMOS Spatial Light Modulators with Flat Beam Profiles
C-P Hsu, C-T Shih, S-Y Wen, Y-H Chien, C-C Hu and H-W Lee
Industrial Technology Research Institute, TW
CMOS, spatial light modulator, wavefront distortion, electrostatic
Two new types of electrostatic grating light modulators (GLMs) are proposed, designed, and analyzed here for improvement on optical wavefront distortion. The proposed GLMs consist different microbeam structures with spring-like legs to improve the flatness of the reflective surfaces. Finite element simulations are conducted to investigate the electro-mechanical behaviors with different geometrical parameters. For 200um long beams, the proposed designs have larger radius of curvature up to 200-900mm that can provide flat reflective surfaces. To obtain the real diffractive phenomenon, the effect of bottom electrode reflection is considered in optical simulations. Simulation results show the proposed designs improve the surface flatness and wavefront distortion significantly. The proposed designs have less energy residue at 0th mode to only 1/3 of that caused by conventional clamped-clamped beams of 200um long. The optimal size of inter-ribbon gap of 0.6um is found also. TSMC 0.35_m mixed signal 2P4M polycide CMOS process is used to fabricate the proposed multi-layered devices with 0.6um gaps.
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Nanotech 2005 Conference Program Abstract