Impact of speckle-beacon size on wavefront sensing and adaptive optics control in volume turbulence

A wave-optics-based numerical simulation analysis of the impact of speckle-beacon size on the performance of an adaptive optics (AO) system operating in volume atmospheric turbulence is presented. For clarity, the speckle beacon was represented by a laser beam of a super-Gaussian profile, scattered off an extended flat target with Lambertian surface roughness. The control loop of the AO system included a high-resolution scintillation-resistant multi-aperture phase contrast wavefront sensor (MAPCO WFS), an ideal (infinite-resolution) wavefront corrector, and phase-conjugation (PC) type controllers utilizing either conventional PC or advanced speckle-average (SA) PC control algorithms. The results obtained show that the use of the advanced control algorithms makes it possible to partially mitigate the target-induced speckle effects and turbulence-induced wavefront aberrations for extended beacons, the size of which is comparable to or even exceeds the diffraction-limited beam spot size of the corresponding laser beam projection system.