Stray Light Analysis and Suppression of Taiji Telescope for Space Gravitational Wave Detection Based on Phase Noise Requirement

Abstract

The telescope is the core device for space gravitational wave detection. It is responsible for receiving signal light and emitting outgoing light simultaneously. When the high-energy outgoing laser passes through the telescope, it would produce stray light, which would interfere with the phase measurement and generate phase noise. Therefore, it is necessary to analyze and suppress the stray light of the telescope. In this paper, the requirement of point source transmittance (PST) of the Taiji telescope is obtained through theoretical derivation, which is less than 4×10−10. Through a complete analysis of stray light, we determined that the M4 was the largest source of stray light under the condition that the roughness of each optical surface is equal, which accounted for 67.22%. We also determined the most lenient requirements for surface roughness σλ, and found that when σλ of the M1, M2, M3, and M4 were 20 Å, 4 Å, 1 Å, and 1 Å, respectively, the PST was 3.89×10−10, which met the PST requirement. Next, we calculated the effect of particulate contamination on the PST, and based on the results of our analysis, we determined that the cleanliness level of the testing and storage environment of the Taiji telescope was better than 300. Finally, we evaluated the changes in the PST caused by the damage of micrometeoroids, and the analysis results showed that the stray light level would not change significantly during the service period of the Taiji Telescope.