In this paper, the design and simulation of a dual-mode Aluminum MEMS micromirror device are proposed. The dual-mode micromirror can work in either torsional or piston modes, depending on the voltage scheme applied to the bottom driving electrodes. The working principle and performance of the micromirror are analyzed. Based upon the analysis, a set of optimized micromirror design parameters is suggested, and the corresponding performance of the micromirror design is reported. According to the analysis, the mirror can deflect for a maximum controllable displacement of 1.3μm in its piston mode, and rotate for a maximum controllable angle of ±3.6° in its torsional mode. If the micromirror works in digital operation in its torisional mode, a maximum rotation angle of ±7.8° can be achieved. ANSYS FEM method is used to simulate the first five vibrational modes and the corresponding resonant frequencies of the micromirror. The micromirror is to be fabricated with thick photoresist sacrificial layer technique. The proposed micromirror can be used to modulate the phase as well as the direction of the incident light due to its dual-mode modes.
Keywords: Microelectromechanical Systems (MEMS), Spatial Light Modulator (SLM), micromirror, piston mirror, torsional mirror
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