The combined use of adaptive optics and nonlinear optical wavefront reversal techniques to compensate for turbulent distortions when focusing laser radiation on distant objects

Approaches to constructing a mock-up of a system for focusing laser radiation on distant objects using both adaptive optics elements and nonlinear-optical wavefront reversal methods providing compensation for turbulent distortions are considered. Numerical calculations were preliminarily performed, in which the split-step method was used as a numerical method for solving a second-order partial differential wave equation for the complex amplitude of the wave field of a laser beam. This method, combined with methods of spectral-phase Fourier transforms and statistical tests, is the most effective way to obtain reliable quantitative results for solving engineering problems of atmospheric wave optics. Quantitative data are obtained on the effect of turbulent atmospheric distortions along propagation paths on the main parameters of coherent laser beams – focusing, effective average radius, and the proportion of the beam energy in its diffraction spot. The preliminary results obtained of the system mock-up performance confirm the conclusions of the theory.

Reconstruction of wavefront distorted by atmospheric turbulence using a Shack-Hartman sensor

The reconstruction of a wave front containing random phase distortions of the light field is considered. The reconstruction is performed by a Hartmann method based on the approximation of the wave function by Zernike polynomials using estimates of local slopes. The slope values depend on the algorithms by which they are determined. The number of slopes is proportional to the number of focal spots recorded in the plane of the receiving device, which varies depending not only on the raster dimension, but also on the parameters of turbulence, design features of the receiving devices, as well as being restricted by the orthogonality of Zernike polynomials. Results of numerical experiments are given, which will be taken into account when creating adaptive optics systems for correcting strong turbulent distortions of the optical radiation.