Local readout enhancement for detuned signal-recycling interferometers

TL;DR

This paper proposes a local readout scheme for detuned signal-recycling interferometers, enhancing low-frequency sensitivity by measuring the front mirror's motion, inspired by the optical-bar concept, and demonstrates its application to improve Advanced LIGO's performance.

Contribution

It introduces a local readout scheme that integrates the optical-bar concept into second-generation interferometers, significantly improving low-frequency quantum noise performance.

Findings

Enhanced low-frequency sensitivity in optical-spring interferometers.

Applicable to improve Advanced LIGO's detection capabilities.

Feasible implementation with current technology.

Abstract

Motivated by the optical-bar scheme of Braginsky, Gorodetsky and Khalili, we propose to add to a high power detuned signal-recycling interferometer a local readout scheme which measures the motion of the arm-cavity front mirror. At low frequencies this mirror moves together with the arm-cavity end mirror, under the influence of gravitational waves. This scheme improves the low-frequency quantum-noise-limited sensitivity of optical-spring interferometers significantly and can be considered as a incorporation of the optical-bar scheme into currently planned second-generation interferometers. On the other hand it can be regarded as an extension of the optical bar scheme. Taking compact-binary inspiral signals as an example, we illustrate how this scheme can be used to improve the sensitivity of the planned Advanced LIGO interferometer, in various scenarios, using a realistic classical-noise budget. We also discuss how this scheme can be implemented in Advanced LIGO with relative ease.