Analysis of parametric resonances in comb-driven microscanners

Abstract

Dynamic behavior of a comb-driven torsional microscanner is governed by a nonlinear parametric differential equation. Theoretically, such systems have multiple resonances located near the integer fractions of twice the mechanical resonance frequency. The number of observable parametric resonances strongly depends on the damping of the system, whereas the stable and unstable operating regions are determined by drive-voltage and drive-frequency. In atmospheric pressure, only first few of these parametric resonances are observable within the operation voltage range of the devices. This paper explores the effect of damping on the various characteristics of parametric resonances and some unusual scanner behavior rarely seen in mechanical structures. A numerical and an analytical model for comb-driven microscanners are presented. Frequency responses of various devices are experimentally measured inside a vacuum chamber at different ambient pressures ranging from atmospheric pressure to 30 mTorr. Experimental results are compared with analytical and simulation results.