Adaptive optics compensation for propagation through deep turbulence: a study of some interesting approaches

Abstract

Scintillation and anisoplanatism significantly degrade a laser transmitter system or an imaging system when the optical field is required to propagate through deep turbulence. Here turbulence is defined as deep turbulence when the Rytov number is very much greater than 1 and the isoplanatic patch size is much smaller than λ/D, the diffraction limit. In this region a point beacon is of little use for imaging applications and a finite-sized beacon limits performance for both transmission and imaging because almost any finite-sized beacon is many isoplanatic patch sizes across and exhibits a significant level of beacon anisoplanatism. As a consequence, conventional adaptive optics techniques are of little value. To address this situation, five approaches are considered. These approaches include beacon deconvolution, Zernike tomography, gradient descent tomography (GDT), irradiance redistribution branch cut multiconjugate adaptive optics compensation, and minimum energy loss eigenfield propagation. GDT appears to have the most promise as it does not require a conventional wavefront sensor.