Systematic search of laser and phase modulation noise coupling in heterodyne interferometry

TL;DR

This paper develops an analytical framework to systematically identify and analyze noise couplings in heterodyne interferometry used in space-based gravitational wave detectors, focusing on phase modulation and laser phase noise.

Contribution

It introduces a novel analytical approach to detect and quantify noise couplings in heterodyne interferometry, including high-frequency laser phase noise, validated by numerical experiments.

Findings

Framework successfully captures major noise couplings.

Derived noise requirements for laser and phase modulation in LISA-like setups.

Validated analytical results with numerical experiments.

Abstract

Heterodyne interferometry for precision science often comes with an optical phase modulation, for example, for intersatellite clock noise transfer for gravitational wave (GW) detectors in space, exemplified by the Laser Interferometer Space Antenna (LISA). The phase modulation potentially causes various noise couplings to the final phase extraction of heterodyne beatnotes by a phasemeter. In this paper, in the format of space-based GW detectors, we establish an analytical framework to systematically search for the coupling of various noises from the heterodyne and modulation frequency bands, which are relatively unexplored so far. In addition to the noise caused by the phase modulation, the high-frequency laser phase noise is also discussed in the same framework. The analytical result is also compared with a numerical experiment to confirm that our framework successfully captures the major noise couplings. We also demonstrate a use case of this study by taking the LISA-like parameters as an example, which enables us to derive requirements on the level of the laser and phase modulation noises in the high frequency regimes.