An inverse-design-based arm locking controller for space gravitational wave detector

Abstract

Since gravitational waves are extremely weak, the frequency noise of the lasers in space-based gravitational wave detectors need to be substantially reduced. One of the key technologies for laser frequency reduction is arm locking. Currently, all the reported controllers in arm locking have an inherent tradeoff between the frequency noise suppression ratio at low frequencies and the noise gain at high frequencies. In this paper, for the first time the inverse design idea is introduced into arm locking controller. By utilizing a multi-parameter co-optimization scheme, the frequency noise suppression ratio in the science band (0.1 mHz to 1 Hz) and the noise gain above the science band can be optimized simultaneously. This work can be generalized to different kinds of arm locking controller design and will effectively improve the sensitivity of the space-based gravitational wave detector.