Self-modulated multimode silicon cavity optomechanics

TL;DR

This paper demonstrates how self-pulsing in silicon cavity optomechanics enables stable, high-amplitude oscillations of multiple mechanical modes despite mode competition and non-harmonic frequencies, advancing multi-phonon source control.

Contribution

It introduces a self-modulation mechanism that synchronizes multiple mechanical modes in silicon cavities, overcoming mode competition and enabling complex multi-phonon dynamics.

Findings

Self-pulsing adapts to mechanical perturbations, stabilizing multiple modes.

High-amplitude, coherent oscillations are achieved in non-harmonic regimes.

Numerical models accurately predict complex intra-cavity dynamics.

Abstract

Multimode cavity optomechanics, where multiple mechanical degrees of freedom couple to optical cavity modes, provides a rich platform for exploring nonlinear dynamics and engineering complex interactions. In this work, we investigate the interplay between two mechanical modes with similar characteristics and a self-induced nonlinear modulation of intra-cavity power (self-pulsing) driven by free-carrier dispersion and thermo-optic effects in silicon. Notably, the self-pulsing dynamics adapts to the optomechanically induced perturbations from both mechanical modes, enabling simultaneous synchronous pumping and driving them into a stable state characterized by high-amplitude, self-sustained, and coherent oscillations. This result effectively overcomes the strong mode competition typically observed in modes with similar spatial distributions and frequency scales. Remarkably, this regime is achieved even when the mechanical frequencies do not satisfy a harmonic relation, leading to quasi-periodic or chaotic intra-cavity power dynamics, while the mechanical modes maintain coherent, high-amplitude oscillations. These results, supported by a numerical model that accurately predicts the dynamics of the system, open new pathways for the generation and control of multi-phonon coherent sources in chip-integrated silicon platforms.