Analysis on the coupling effect of wavefront distortion and pointing misalignment in space laser interferometry

Space-based gravitational wave detection aims to measure gravitational waves with strains of down to 10(-20) in 10(-4) Hz similar to 1 Hz frequency band. In order to achieve this measurement sensitivity, inter-satellite laser interferometry with picometer precision for an armlength of 10(8) similar to 10(9) m is required. However, the coupling of the transmitting-beam misalignment and the wavefront distortion results in a non-negligible measurement error of intersatellite laser interferometry. Considering a wavefront distortion model composed of the first 55 terms of Zernike polynomials, we analyze the coupling effect of beam misalignment and wavefront distortion in both analytical and numerical methods. Calculation results show that the position of the stationary point is mainly determined by defocus, astigmatism and coma of the wavefront distortion of the transmitting beam. Moreover, a large defocus and small coma are preferred to achieve a better alignment of the stationary pointing direction with the inter-satellite line-of-sight, such that the coupling noise and received laser power can be optimized.

Automated summary

Space-based gravitational wave detection requires high measurement sensitivity using inter-satellite laser interferometry, but misalignment and wavefront distortion of the laser transmitting beam can impact the accuracy of the interferometer measurements.