Nanotech 2010

Arrayed, Piezoelectrically-Actuated Mirrors and Gratings for Spectrometer

S-J Chen, D. Chi, J. Lo, E.S. Kim
University of Southern California, US

Keywords: MEMS spectrometer, piezoelectric, actuated micromirror, grating, mirror array

Abstract:

This paper describes a technology for a compact spectrometer based on a 2D piezoelectric mirror and/or grating array. The piezoelectric mirror/grating array is composed of angularly movable, 2-D array of micromirrors/microgratings that is supported on piezoelectric cantilevers, and can be driven piezoelectrically with controllable tilt angle in both upward and downward directions. A large reflecting/diffractive surface is obtained through a combination of the small-sized mirrors/gratings that are surface-micromachined without fabrication difficulties associated with a large size mirror/grating. The fabricated piezoelectric mirror array was applied to the spectrum imaging by aligning the mirror array to a fixed Al grating with pitch of 500 nm and grating depth of 100 nm. The diffraction efficiency of the combination was measured for three different diffraction orders. We also measured the angular displacement of the mirror array as a function of frequency. With 10 Vpeak-to-peak sinusoidal wave input, the mirror structure was measured to have 420 nm peak-to-peak displacement at its first resonant frequency, which corresponds to 0.025°/V. The first resonant frequency of the mirror supported by the piezoelectric cantilever was around 5.4 kHz. Furthermore, we fabricated a piezoelectric grating array, which can be integrated to form a wavelength-selectable, compact 2D spectrometer.
 
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