Enhanced optomechanical readout using optical coalescence

TL;DR

This paper introduces a novel scheme called optical coalescence that significantly enhances the sensitivity of optomechanical readout by exploiting interference effects in a modified Fabry-Pérot cavity with a movable middle reflector.

Contribution

It demonstrates how placing a highly reflective element inside a symmetric Fabry-Pérot cavity can induce optical coalescence, leading to improved optomechanical measurement sensitivity.

Findings

Enhanced frequency shift of cavity transmission peaks due to optical coalescence

Strong modification of cavity response function by a middle reflector

Potential for improved optomechanical sensing applications

Abstract

We present a scheme to strongly enhance the readout sensitivity of the squared displacement of a mobile scatterer placed in a Fabry-P\'erot cavity. We investigate the largely unexplored regime of cavity electrodynamics in which a highly reflective element positioned between the end mirrors of a symmetric Fabry-P\'erot resonator strongly modifies the cavity response function, such that two longitudinal modes with different spatial parity are brought close to frequency degeneracy and interfere in the cavity output field. In the case of a movable middle reflector we show that the interference in this generic "optical coalescence" phenomenon gives rise to an enhanced frequency shift of the peaks of the cavity transmission that can be exploited in optomechanics.