Tilt-to-length coupling noise suppression based on transformation of q parameters of Gaussian beams in spaceborne gravitational wave detection

Abstract

Suppression of the coupling of unavoidable angular spacecraft jitter into the longitudinal displacement measurement, known as tilt-to-length (TTL) coupling, is crucial for realizing the required sensitivity of picometer /Hz1/2 level within the frequency range of 1 mHz–1 Hz in spaceborne gravitational wave detection. In this paper, we propose a novel method to suppress the TTL coupling between two Gaussian beams demonstrated by simulation. Our approach involves placing a set of lenses with specific focal lengths at proper locations to match the q parameters of the two interfering beams based on our design principle. The results demonstrate a significant reduction in TTL coupling and testify the effectiveness of our proposed approach. TTL coupling factors below 0.21 μ m rad−1 with ideal parameters and below 4.65 μ m rad−1 with focal length error set at 1% as well as installation error (lateral-alignment and longitudinal-alignment errors) set at 10 μ m are achieved for beam tilts within ±300μrad .