Real-Time Correction of a Laser Beam Wavefront Distorted by an Artificial Turbulent Heated Airflow

Abstract

This paper presents a FPGA-based closed-loop adaptive optical system with a bimorph deformable mirror for correction of the phase perturbation caused by artificial turbulence. The system’s operating frequency of about 2000 Hz is, in many cases, sufficient to provide the real-time mode. The results of the correction of the wavefront of laser radiation distorted by the airflow formed in the laboratory conditions with the help of a fan heater are presented. For detailed consideration, the expansion of the wavefront by Zernike polynomials is used with further statistical analysis based on the discrete Fourier transform. The result of the work is an estimation of the correction efficiency of the wavefront distorted by the turbulent phase fluctuations. The ability of the bimorph adaptive mirror to correct for certain aberrations is also determined. As a result, it was concluded that the adaptive bimorph mirrors, together with a fast adaptive optical system based on FPGA, can be used to compensate wavefront distortions caused by atmospheric turbulence in the real-time mode.

Wavefront control with high-spatial cartridge-type piezostack deformable mirror

“…Prepared base elements sized 26 x 26 x 5.5 mm were assembled into a package with active layers (26 x 26 x 0.5 mm), after which the compression welding of the piezoceramic block (6) took place. The assembled and welded block was again subjected to mechanical processing (grinding of the end surfaces) (7), after which it was sawn into separate modules (8).…”

“…Various methods could be used to mitigate influence of the atmospheric turbulence on the wavefront of the laser beam propagated over the distance. The most popular of them are spatial or time diversity [2,3] , coherent combining [4] , coding [5] or adaptive optics techniques [6,7] . Among all of these approaches latter proved its efficiency for a lot of applications: free-space communications systems [8], space debris removal [9] , material processing [10] , UAV laser destruction [11] and so on [12][13][14] .…”

Cartridge-type piezostack deformable mirror with reduced cross-section of control elements

“…To manipulate the properties of the laser beam (intensity distribution, focusability, phase distortions compensation) a lot of techniques could be used: hardware (like focusators [1] , shapers [2,3] , adaptive optics methods [4][5][6][7][8] ), software (luckyimaging [9][10][11] , global processing [12] ) or using both techniques (for example, phase diversity [13,14] ). Main goal of using such devices or methods is mitigate undesirable effects on the laser beam propagated over distance.…”

Stroke simulation of control elements in cartridge-type deformable mirror for correction of aberrations of laser radiation passed through turbulent medium

“…Former (absorption, scattering) phenomena could be overcome by optimization of the optical wavelength [1] . To improve the quality of optical beam impaired due to the turbulence a lot of various techniques could be used such as: aperture averaging [2] , diversity [3] , adaptive optics [4,5] , modulation and coding [6] .…”