Laser probing of nonlinearities in MEMS resonators

Nonlinear effects have become an important issue in microacoustic component development to improve performance. In addition to the modeling, simulations and electrical characterization tools, a direct method for observing the nonlinear vibration fields in these components would be beneficial in the device design. We use laser probing for studying the nonlinear acoustic behavior in two square-extensional (SE) mode MEMS resonators, whose electrically measured SE-resonances compress above a certain, unexpectedly low, input drive power level. In the laser probe measurements, the vibration amplitude of the SE mode is observed to nearly saturate above this drive power level, and simultaneously another mode at a different frequency is excited. It is also observed that the nonlinearly excited modes are different in the two resonators, and each resonator has a distinct nonlinear behavior.