Numerical comparison of adaptive optics correction based on stochastic parallel gradient descent and phase conjugate in scintillation conditions

Abstract

Adaptive optics (AO) systems with wavefront sensors are based on the phase conjugate (PC) principle. These systems do not work effectively when the scintillation intensity in the receiver aperture becomes significant. AO correction technique based on stochastic parallel gradient descent (SPGD) control algorithm is an alternative approach which does not depend on wavefront sensor but optimizes the performance metric directly. In this study, we established a simulation model for an SPGD–AO system in which the SPGD optimisation algorithm was applied to control the tip-tilt and the deformable mirrors to correct the aberration in several turbulence scenarios. The performances of the SPGD–AO and the PC–AO correction schemes were tested in different scintillation conditions based on numerical simulations of dynamic turbulence. In weak scintillation conditions, the effects of the SPGD–AO correction were as accurate as those of the PC–AO correction, but upon scintillation increasesσR2>1, the SPGD–AO yielded a significant correction effect compared to PC correction. The results also showed that SPGD did not require any wavefront phase information, but it was very effective for discontinuous phase correction.