Picometer-level quadrangle optical bonding bench for testing interferometric technologies in TianQin

TL;DR

This paper presents a novel quadrangle optical bench with picometer-level stability for testing interferometric technologies essential for space-based gravitational wave detection, validated through experiments demonstrating high precision and low noise.

Contribution

Introduces a simplified quadrangle quasi-monolithic optical bench that expands testing capabilities for TianQin's interferometric techniques, building on previous hexapod designs.

Findings

Achieves picometer-level optical pathlength stability and phase resolution.

Laser transponder link residual noise below 10^{-4} rad/Hz^{1/2} above millihertz.

Minimal coupling of laser sideband modulation to measurements.

Abstract

Interferometric techniques are crucial for space-based gravitational wave detection, requiring a picometer-level stable optical bench, precise phasemeter, interstellar transponder low-light phase locking, and laser sideband communication. These technologies must be rigorously tested on the ground before deployment in space. The AEI group has previously developed a picometer-stable hexapod optical bench to verify the linearity and precision of phase extraction for LISA. In this paper, we introduce a quadrangle quasi-monolithic optical bench aimed at simplifying the system and expanding the range of tested interferometric techniques for TianQin. Experimental results demonstrate that the system achieves picometer-level optical pathlength stability and phase resolution over a large dynamic range. In the laser transponder link test, the light phase-locked residual noise is lower than ${\rm 10^{-4}\,rad/Hz^{1/2}}$ above millihertz frequency range, and the laser sideband modulation has no significant coupling to the measurements in the ${\rm mHz-Hz}$ band. These results provide critical technical validation for the implementation of future gravitational wave detection in space.