Nonlinearity-induced synchronization enhancement in micromechanical oscillators

An autonomous oscillator synchronizes to an external harmonic force only when the forcing frequency lies within a certain interval around the oscillator's natural frequency. Under ordinary conditions, the width of this ``synchronization range'' decreases when the oscillator's self-sustained amplitude grows, constraining synchronized motion of micro- and nanomechanical resonators to narrow frequency and amplitude bounds. In this talk, we will show that {\it nonlinearity} in the oscillator can be exploited to manifest a regime where the synchronization range {\it increases} with increasing oscillation amplitude. We demonstrate this regime experimentally with a self-sustained micromechanical oscillator, revealing an increase in the synchronization range by orders of magnitude over that expected for a linear oscillator. We provide analytical results which show that nonlinearities are the key determinants of this enhancement. Our results suggest a new strategy to enhance synchronization of micromechanical oscillators by capitalizing on their intrinsic nonlinear dynamics.