Sensitivity limitations in optical speed meter topology of gravitational-wave antennae

TL;DR

This paper analyzes the sensitivity limits of optical speed meter topologies for gravitational-wave detectors, showing they can surpass the Standard Quantum Limit but face challenges with signal recycling and optical losses.

Contribution

It provides a detailed analysis of the ultimate sensitivity of speed meter interferometers and discusses practical implementation considerations for gravitational-wave detection.

Findings

Speed meters can beat the SQL by up to a factor of 3 wideband and 10 narrowband.

Signal recycling is difficult to implement in speed meter topology.

Achieving the ultimate sensitivity requires about 1 MW circulating power.

Abstract

The possible design of QND gravitational-wave detector based on speed meter principle is considered with respect to optical losses. The detailed analysis of speed meter interferometer is performed and the ultimate sensitivity that can be achieved is calculated. It is shown that unlike the position meter signal-recycling can hardly be implemented in speed meter topology to replace the arm cavities as it is done in signal-recycled detectors, such as GEO 600. It is also shown that speed meter can beat the Standard Quantum Limit (SQL) by the factor of $\sim 3$ in relatively wide frequency band, and by the factor of $\sim 10$ in narrow band. For wide band detection speed meter requires quite reasonable amount of circulating power $\sim 1$ MW. The advantage of the considered scheme is that it can be implemented with minimal changes in the current optical layout of LIGO interferometer.