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Optical Knife-Edge Displacement Measurement with Sub-Picometer Resolution for RF-MEMS

Published

Author(s)

Vikrant J. Gokhale, Jason J. Gorman

Abstract

Optical knife-edge measurements can be used to quantify in-plane displacements of microstructures vibrating at high frequencies. This work presents an analytical model and experimental results for optical knife-edge measurements that demonstrate precise displacement measurements for electrostatic MEMS resonators with a narrow actuation gap. The model is experimentally validated using silicon RF-MEMS resonators with predominantly in-plane motion at frequencies ranging from 13 MHz to 895 MHz. It is also shown that high-resolution spatial mapping of displacement mode shapes for fundamental and higher-order vibration modes is possible. Mode shape mapping reveals the true dynamics of fabricated devices, and can be used to improve device performance. The optical knife-edge measurements have a resolution as low as 455 fm/√Hz at 13.6 MHz, and under 1 pm/√Hz up to 1.4 GHz. This work expands the scope of the knife-edge technique to work with any type of MEMS resonator, improves the resolution by at least a factor of 2, and increases the demonstrated frequency range by a factor of 60.
Citation
Journal of Microelectromechanical Systems

Keywords

Optical knife edge, micromechanical resonator, displacement measurement, vibration measurement, radio frequency, mode shapes

Citation

Gokhale, V. and Gorman, J. (2018), Optical Knife-Edge Displacement Measurement with Sub-Picometer Resolution for RF-MEMS, Journal of Microelectromechanical Systems, [online], https://doi.org/10.1109/JMEMS.2018.2861322 (Accessed May 8, 2021)
Created August 13, 2018, Updated November 10, 2018