Time-Delay Interferometry with optical frequency comb

TL;DR

This paper proposes a novel method using optical frequency combs to cancel microwave phase noise in space-based gravitational wave detectors, simplifying the system and improving sensitivity without additional modulation or ultra-stable clocks.

Contribution

It introduces a technique to directly cancel microwave noise in heterodyne measurements using optical frequency combs, eliminating the need for complex modulation and extra clocks.

Findings

Microwave noise can be effectively canceled using modified second-generation TDI.

The method simplifies the system by removing the need for laser beam modulation.

Enhanced sensitivity in gravitational wave detection is achievable with this approach.

Abstract

Heterodyne laser phase measurements in a space-based gravitational wave interferometer are degraded by the phase fluctuations of the onboard clocks, resulting in unacceptable sensitivity performance levels of the interferometric data. In order to calibrate out the clock phase noises it has been previously suggested that additional inter-spacecraft phase measurements must be performed by modulating the laser beams. This technique, however, considerably increases system complexity and probability of subsystem failure. With the advent of self-referenced optical frequency combs, it is possible to generate the heterodyne microwave signal that is coherently referenced to the onboard laser. We show in this case that the microwave noise can be cancelled directly by applying modified second-generation Time-Delay Interferometric combinations to the heterodyne phase measurements. This approach avoids use of modulated laser beams as well as the need of additional ultra-stable oscillator clocks.