Detection of weak forces based on noise-activated switching in bistable optomechanical systems

TL;DR

This paper introduces a method for detecting weak forces using noise-activated switching in bistable optomechanical systems, leveraging the modulation of cavity resonance to amplify signals.

Contribution

It develops a quantitative model for force detection based on bistable optomechanical systems and compares its performance to linear regime detection.

Findings

Switching rates depend on cavity detuning.

The model predicts power gain and SNR for weak forces.

Enhanced detection sensitivity over linear regime.

Abstract

We propose to use cavity optomechanical systems in the regime of optical bistability for the detection of weak harmonic forces. Due to the optomechanical coupling an external force on the mechanical oscillator modulates the resonance frequency of the cavity and consequently the switching rates between the two bistable branches. A large difference in the cavity output fields then leads to a strongly amplified homodyne signal. We determine the switching rates as a function of the cavity detuning from extensive numerical simulations of the stochastic master equation as appropriate for continuous homodyne detection. We develop a two-state rate equation model that quantitatively describes the slow switching dynamics. This model is solved analytically in the presence of a weak harmonic force to obtain approximate expressions for the power gain and signal-to-noise ratio that we then compare to force detection with an optomechanical system in the linear regime.