Local-Oscillator Noise Coupling in Balanced Homodyne Readout for Advanced Gravitational Wave Detectors

TL;DR

This paper investigates how local oscillator noise affects balanced homodyne detection in large-scale gravitational wave detectors, highlighting implementation challenges and potential issues for future upgrades.

Contribution

It derives implementation requirements for local oscillator noise coupling in balanced homodyne detection for gravitational wave detectors and analyzes potential issues for large-scale applications.

Findings

Identifies local oscillator noise coupling mechanisms.

Highlights challenges in scaling balanced homodyne detection.

Provides implementation guidelines for future detectors.

Abstract

The second generation of interferometric gravitational wave detectors are quickly approaching their design sensitivity. For the first time these detectors will become limited by quantum back-action noise. Several back-action evasion techniques have been proposed to further increase the detector sensitivity. Since most proposals rely on a flexible readout of the full amplitude- and phase-quadrature space of the output light field, balanced homodyne detection is generally expected to replace the currently used DC readout. Up to now, little investigation has been undertaken into how balanced homodyne detection can be successfully transferred from its ubiquitous application in table-top quantum optics experiments to large-scale interferometers with suspended optics. Here we derive implementation requirements with respect to local oscillator noise couplings and highlight potential issues with the example of the Glasgow Sagnac Speed Meter experiment, as well as for a future upgrade to the Advanced LIGO detectors.