Influence of EOM sideband modulation noise on space-borne gravitational wave detection

TL;DR

This paper analyzes the impact of EOM sideband modulation noise on space-borne gravitational wave detection, deriving strict noise requirements and experimentally verifying a commercial EOM's suitability for LISA.

Contribution

It provides a rigorous analytic expression for modulation noise requirements and experimentally confirms a commercial EOM's capability to meet these standards for GW detection.

Findings

Derived strict modulation noise requirement expression.

Experimental verification of commercial EOM meeting LISA's noise standards.

EOM can support future improved displacement measurement accuracy.

Abstract

Clock noise is one of the dominant noises in the space-borne gravitational wave (GW) detection. To suppress this noise, the clock noise-calibrated time-delay-interferometry (TDI) technique is proposed. In this technique, an inter-spacecraft clock tone transfer chain is necessary to obtain the comparison information of the clock noises in two spacecraft, during which an electro-optic-modulator (EOM) is critical and used to modulate the clock noise to the laser phase. Since the EOM sideband modulation process introduces modulation noise, it is significant to put forward the corresponding requirements and assess whether the commercial EOM meets. In this work, based on the typical Michelson TDI algorithm and the fundamental noise requirement of GW detectors, the analytic expression of the modulation noise requirement is strictly derived, which relax the component indicator need compared to the existing commonly used rough assessments. Furthermore, a commercial EOM (iXblue-NIR-10 GHz) is tested, and the experimental results show that it can meet the requirement of the typical GW detection mission LISA in whole scientific bandwidth by taking the optimal combination of the data stream. Even when the displacement measurement accuracy of LISA is improved to 1 pm/ $\mathrm{Hz^{1/2}}$ in the future, it still meets the demand.