Determination of the vacuum optomechanical coupling rate using frequency noise calibration

TLDR

The vacuum optomechanical coupling rate quantifies the strength of interactions in cavity optomechanical systems, providing a clear figure of merit that eliminates ambiguity in coupling parameters and effective mass definitions. Here we demonstrate and verify a straightforward experimental technique to derive the vacuum optomechanical coupling rate. The method only requires applying a known frequency modulation of the employed electromagnetic probe field and knowledge of the mechanical oscillator's occupation. The technique is experimentally verified for a micromechanical mode in a toroidal whispering‑gallery resonator and a nanomechanical oscillator coupled to a toroidal cavity via its near field.

Abstract

The strength of optomechanical interactions in a cavity optomechanical system can be quantified by a vacuum coupling rate $\vcr$ analogous to cavity quantum electrodynamics. This single figure of merit removes the ambiguity in the frequently quoted coupling parameter defining the frequency shift for a given mechanical displacement, and the effective mass of the mechanical mode. Here we demonstrate and verify a straightforward experimental technique to derive the vacuum optomechanical coupling rate. It only requires applying a known frequency modulation of the employed electromagnetic probe field and knowledge of the mechanical oscillator's occupation. The method is experimentally verified for a micromechanical mode in a toroidal whispering-gallery-resonator and a nanomechanical oscillator coupled to a toroidal cavity via its near field.