A laser frequency-stabilised control system for space-borne gravitational wave detection

Space-borne gravitational wave detectors, including the TAIJI and LISA programs, utilize interstellar transponder laser interferometry technology. The frequency stability of the laser is of utmost importance, as it forms a critical component of laser interferometry systems. Laser frequency noise directly impacts distance measurements' accuracy and contributes to improper data acquisition in gravitational wave detectors. Therefore, the development of a long-stability and high precision laser locking control system tailored for space-borne high-stability laser is essential. This paper presents a laser frequency-stabilized control system based on the Pound-Drever-Hall (PDH) technique, providing a high reliability, automatic locking electronic control system to illustrate the method for space-borne high-stability laser. A large bandwidth, highly reliable automatic frequency stabilization module suitable for space applications was designed and performed on a cavity-stabilized laser. A typical PDH error is generated based on a Fabry-Perot cavity laser stabilization experiment. After the error signal passed through the module's loop filter, the laser is controlled by a low control loop and a fast control loop. The noise in the low-frequency band is emulated by the control circuit. The frequency stabilization system can automatically lock the laser and re-lock it following a loss of locking, in response to signals from photodetectors and camera. This capability ensures the laser's long-term stable operation in orbit, in line with mission requirements. In conclusion, after precise noise analysis and control loop design, A laser frequency stabilization control system demonstrated high long-term frequency locking is designed and implemented. The control system can well fulfill the laser frequency stability requirements. This study advances the design of frequency-stabilized lasers and the development of future applications in space. Moreover, it provides relevant technical verification for subsequent Taiji mission stages.