Numerical Simulation Of Steady-state Thermal Blooming Of Array Composite Beams In Atmosphere

When the high-energy laser transmits in the atmosphere,it will produce the nonlinear thermal blooming effect,resulting in the beam deflection,expansion,distortion and other phenomenon,which reduces the quality of the far-field beam and limits the development and application of high-energy lasers.At present,the study of thermal blooming effect mostly focuses on the steady-state thermal blooming effect in the presence of crosswind,and the wholistic analysis of the steady-state thermal blooming effect in windy,windless and other transmission environments is relatively small.This paper introduces the perturbation method,based on analytical theory,and the phase-screen method,based on numerical simulation,and focuses on the systematic analysis of the steady-state thermal blooming effect in the absence of wind and in the presence of crosswind.the output power of a single-aperture high-energy lasers is limited,and it is difficult to achieve people's increasing expectations.one of the effective methods to obtain high power lasers is the array beam synthesis technology,but there are few simulation studies on the steady-state thermal blooming effect of the arrayed beam.This article will focus on the numerical simulation of the steady-state thermal halo effect of arrayed beams in the atmosphere.From the scalar wave equation,the fluid dynamics equations and the Lorentz-Lorenz relation,his paper systematically introduces two common analysis methods for the study of the thermal halo effect: the perturbation method based on geometric optics and the phase screen method based on wave optics.Give examples of thermal blooming effect in different transmission environments and their respective scope of application.Using the perturbation method and phase-screen method,the steady-state thermal blooming effect in the absence of wind and the presence of crosswind is numerically simulated,and the transmission distance,absorption coefficient,initial power,wind speed and other factors are systematical analyzed for the steady-state thermal blooming effect.Providing theoretical guidance for the simulation of the steady-state thermal blooming effect of arrayed beams.In this paper,the Fourier transform phase screen method is used to simulate the steady-state thermal blooming effect in the transmission of the radial distribution array composite beam under coherent synthesis and incoherent synthesis.Using the evaluation parameters such as the centroid offset of the far field spot,the proportion of power in the bucket,and the peak power density to analyze the effect of transmission distance,absorption coefficient,initial power,and wind speed on the beam quality in the far field of the radial distribution array synthesized high-power laser beam.In this thesis,the effects of sub-beam number and subbeam aperture size on the far-field beam quality of the array composite beam are analyzed.The results show that the beam quality of the coherent array composite beam in the far field is better than that of the non-coherent array synthesis under the condition of the same total output power,close transmission distance,low absorption coefficient and high wind speed.However,with the worsening of the transmission environment,the far-field beam quality of the two tends to be consistent,for the incoherent array beam,increasing the number of subaperture beams can improve the field peak power density of the far-incoherent array beam.Increasing the sub-beam aperture can improve the far-field peak power density and peak power threshold of incoherent array composite beams.For coherent array composite beams,under the condition of close transmission distance,low absorption coefficient and high wind speed.Increasing the number of sub-aperture beams and reducing the aperture of the subbeams can increase the far-field peak power density of a coherent array composite beam.