Arm-length stabilisation for interferometric gravitational-wave detectors using frequency-doubled auxiliary lasers

TL;DR

This paper introduces a method using frequency-doubled auxiliary lasers to pre-stabilize arm cavity lengths in gravitational-wave detectors, significantly reducing noise and aiding lock acquisition.

Contribution

The novel technique employs auxiliary lasers at twice the measurement frequency to improve arm cavity stabilization in interferometric gravitational-wave detectors.

Findings

Reduced length noise to 30 pm rms in a 1.3 m cavity

Successfully transferred control from auxiliary to measurement laser

Enhanced lock acquisition capability in gravitational-wave interferometers

Abstract

Residual motion of the arm cavity mirrors is expected to prove one of the principal impediments to systematic lock acquisition in advanced gravitational-wave interferometers. We present a technique which overcomes this problem by employing auxiliary lasers at twice the fundamental measurement frequency to pre-stabilise the arm cavities' lengths. Applying this approach, we reduce the apparent length noise of a 1.3 m long, independently suspended Fabry-Perot cavity to 30 pm rms and successfully transfer longitudinal control of the system from the auxiliary laser to the measurement laser.