Suppression of coupling between optical aberration and tilt-to-length noise in a space-based gravitational wave telescope.

Coupling between exiting wavefront error of space gravitational wave telescopes and tilt-to-length (TTL) noise affects the measurement accuracy. Using the LISA Pathfinder signal, we analyzed cancellation and superposition of TTL coupling noise under various optical aberrations. We proposed proportion requirements of any two aberrations amplitude when noise was cancelled and an aberration amplitude control requirement when noise was superposed. Taking them as the aberration control requirements of gravitational wave telescope optical system, the exiting wavefront error requirements was reduced while suppressing the TTL coupling noise. A 40× optical telescope system with detection aperture φ=200 mm was designed. The exiting wavefront error was relaxed from 0.02 λ to 0.0496 λ. The maximum coupling coefficient value did not exceed 6.9448 pm/µrad within a pointing jitter angle of ±300 µrad. The proposed approach should be useful in future telescope design.