Abstract
In this paper, we present theoretical and experimental study on the viscous damping of the on-substrate torsional micromirrors, oscillating near the silicon substrates. In the theoretical study, we develop theoretical models and test structures for the viscous damping of the on-substrate torsional micromirrors. From a finite element analysis, we obtain the fundamental modes of the torsional micromirrors, fabricated by the surface-micromachining process. From the electrostatic test of the fabricated devices, rotational velocity of the micromirrors has been measured at the atmospheric pressure using the Mach-Zehnder interferometer system. Experimental damping coefficients have been extracted from the least square fit of the measured rotational velocity within the filter bandwidth of 150kHz. We have compared the theoretical values and the experimental results on the dynamic performance of the micromirrors. The theoretical analysis overestimates the resonant frequency in the amount of 15%, while underestimating the viscous damping in the factors of 10%, respectively.
