Optical design of space gravitational wave detection telescope

In space gravitational wave detection, the telescope is an important part of the space laser interfer-ometry system. The wavefront error at the exit pupil of the telescope is coupled with the Tilt-To-Length(TTL) noise, which becomes the main source of noise in space gravitational wave detection. Firstly, based onthe interference model between a flat-top beam and a Gaussian beam, the Fringe Zernike polynomial is used o characterize the wavefront error at the exit pupil of the telescope, and the LISA Pathfinder (LPF) signal isused to analyze the coupling mechanism of the wavefront error at the exit pupil and the TTL noise. Secondly,the Monte Carlo analysis method is used to study the influence of the proportion of low-order aberrations onthe TTL coupling noise under different numerical wavefront errors, and determine the low-order aberrationproportions which meets the requirements of TTL coupling noise control at the exit pupil in the design of thetelescope optical system under different numerical wavefront errors. Finally, based on the above theoreticalanalysis results and the aberration control requirements, the optical design of the space gravitational wave de-tection telescope is completed. The diameter of the entrance pupil of the telescope is 200 mm, and the RMSvalue of the wavefront error at the exit pupil is 0.01908 lambda. The proportion of low-order aberrations is nothigher than 50%. The analysis results show that the TTL coupling noise does not exceed 8.25 pm/mu rad whenthe beam jitter is within +/- 300 mu rad. Through tolerance analysis, the maximum TTL coupling noise is determ-ined to be 15.50 pm/mu rad, which meets the requirements of space gravitational wave detection