Anomalous dynamic back-action in interferometers

TL;DR

This paper investigates the unique dynamic back-action effects in off dark port signal-recycled Michelson and Michelson-Sagnac interferometers, revealing new regimes of optomechanical cooling, heating, and stable optical springs that could enhance gravitational-wave detectors.

Contribution

It introduces the analysis of anomalous dynamic back-action in interferometers operated off dark port, showing non-zero optical damping at resonance and stable optical springs for gravitational-wave detection.

Findings

Optical damping is non-zero on resonance in Michelson-Sagnac interferometers.

New stability and instability regions around resonance are identified.

Stable optical spring regimes can reduce quantum noise in gravitational-wave detectors.

Abstract

We analyze the dynamic optomechanical back-action in signal-recycled Michelson and Michelson-Sagnac interferometers that are operated off dark port. We show that in this case --- and in contrast to the well-studied canonical form of dynamic back-action on dark port --- optical damping in a Michelson-Sagnac interferometer acquires a non-zero value on cavity resonance, and additional stability/instability regions on either side of the resonance, revealing new regimes of cooling/heating of micromechanical oscillators. In a free-mass Michelson interferometer for a certain region of parameters we predict a stable single-carrier optical spring (positive spring and positive damping), which can be utilized for the reduction of quantum noise in future-generation gravitational-wave detectors.