Robustness analysis and controller design of arm-locking system in space-based gravitational wave detectors
Phys. Rev. D 113, 024054 – Published 23 January, 2026
DOI: https://doi.org/10.1103/5cb7-pvpw
Abstract
Arm-locking frequency stabilization is a key technique for suppressing laser frequency noise in space-based gravitational-wave detectors. The robustness of the arm-locking control loop is crucial for maintaining laser frequency stability, which directly impacts the accuracy of gravitational-wave measurements. In this work, a parametric stability analysis framework is developed by combining the D-subdivision theory with the Semi-Discretization method to map the stability regions of arm-locking systems in the parameter space and to identify their critical stability boundaries. Based on the frequency-domain characteristics, a robust arm-locking controller is designed to enhance loop stability under parameter perturbations. Theoretical analysis and time-domain simulations confirm that the proposed controller maintains closed-loop stability and realizes suppression of laser frequency noise against parameter perturbation.
