The Length Sensing and Control of the Ground-based Laser Interferometric Gravitational Wave Detectors postprint

Abstract: During the operation of ground-based laser interferometric gravitational wave detectors, the internal optical systems are subject to various noise disturbances, resulting in uncontrollable displacements. To enhance the sensitivity of the detectors and enable the detection of faint gravitational wave signals, it is imperative to employ a length sensing and control system. This system ensures that multiple optical cavities within the detector remain in resonance, thereby facilitating the design of gravitational wave signal readout schemes. Beginning with the configuration of laser interferometric gravitational wave detectors, this paper outlines the fundamental principles of length feedback control and parameter design criteria. Drawing on specific parameters of the Advanced LIGO, Advanced Virgo, and KAGRA control systems currently in operation, a detailed exposition is provided on the working principles and applications of length sensing and control systems in gravitational wave detectors.