Ph.D Thesis

Ph.D StudentZaitsev Stav
SubjectForced and Self-Excited Oscillations in Nonlinear
Micromechanical Resonators
DepartmentDepartment of Electrical and Computer Engineering
Supervisor ASSOCIATE PROF. Eyal Buks


We investigate a variety of nonlinear phenomena in micromechanical resonators, with special emphasis on coupling to optical resonance cavities.

First, we study forced and self-excited oscillations in an optical cavity, which is formed between a fiber Bragg grating that serves as a static mirror and between a freely suspended metallic mechanical resonator that serves as a moving mirror. In the domain of small amplitude mechanical oscillations, we find that the optomechanical coupling is manifested as changes in the effective resonance frequency, damping rate and cubic nonlinearity of the mechanical resonator. Moreover, self-excited oscillations of the micromechanical mirror are observed above a certain optical power threshold. A comparison between the experimental results and a theoretical model that we have derived and analyzed yields a good agreement.

Next, we turn to investigate the nonlinearities of micromechanical resonators that are not optically induced. We employ a doubly clamped micromechanical beam oscillator, which exhibits nonlinearity in both elastic and dissipative properties. The dynamics of the oscillator is measured in both frequency and time domains and compared to theoretical predictions based on a Duffing-like model with nonlinear dissipation. We especially focus on the behavior of the system near bifurcation points. The results show that nonlinear dissipation can have a significant impact on the dynamics of micromechanical systems.