Propagation And Damage Effect Modeling Of Phased Corrected High Energy Laser In The Atmosphere

High-energy laser weapons use laser beam directly hit target or make the target component failure for military purpose,and which has the advantages of high effectiveness-cost ratio,fast reaction speed,long strike distance,and destruction after discovery with no time delay.The high energy laser weapon will play an important role in the future war,and thus many countries are focusing the research and deployment of high-energy laser weapons.However,the laser will be affected by atmospheric turbulence and thermal blooming in the transmission process,which makes the beam quality become worse and weaken the final damage effect.Therefore,it is necessary to pre-correct the laser at the laser weapon transmitter system to improve the beam quality at the target point and improve the damage efficiency.A full-link propagation and damage model of phase-corrected high energy laser involving turbulence effect,thermal blooming and laser-matter interaction studied in this work,it is expected to help the initial design analysis of high-energy laser weapons development.The main research contents are described as follows:Firstly,the related theory of atmospheric turbulence and the method of constructing the phase screen is presented.The low frequency harmonic compensation method for power spectrum inversion is verified,then the multiphase screen method of atmospheric laser transmission is introduced.The transmission of gaussian beam in vacuum is simulated and compared with the theory to prove the validity of the model.According to the distribution characteristics of atmospheric turbulence with height during the vertical transmission of high-energy laser,under the Hufnagel-Valley typical atmospheric turbulence profile model,the equivalent Rytov index distribution scheme is selected for simulation.The light spots at the target under short and long exposures are simulated.Secondly,the atmospheric absorption,attenuation effects and the thermal blooming effect is introduced.The equivalent weighted average is used to research the steadystate thermal blooming effect of the gaussian beam during vertical transmission and the thermal blooming model is established.The effects of different transmission distances,beam radius,and emission power on the thermal blooming effect are analyzed.The results show that the thermal blooming effect increases along with the transmission distance,and the laser intensity increase.Then the steady-state thermal blooming effect of the plane waves with different radii is simulated,and compared with the gaussian beam,the thermal distortion characteristics are different.The multiphase screen method is used to simulate the gaussian beam with different radii by considering both of the turbulence and thermal blooming effects.It was found that the thermal distortion is many affected by the beam radius in short exposure spot,and its long exposure spot is similar to the thermal blooming spot of the same radius gaussian beam.Thirdly,the beam quality evaluation method for a phase conjugation corrected high energy laser is investigated from the point of view of atmospheric turbulence,thermal blooming effect and their comprehensive effect.The precorrection effect of atmospheric turbulence of gaussian beams with different radii is evaluated using on-axis peak Strehl ration and beam quality index under long exposure.The precorrection effect of thermal blooming is mainly described by the peak offset and beam quality index.The precorrection obtained the best correction effect from the points of the peak offset and beam quality index for small thermal distortion.The comprehensive phase corrected effect of atmospheric turbulence and thermal blooming is also affected by the strength of thermal distortion and the correction effects is investigated under different correction levels.Finally,the interaction of high-energy laser and materials is introduced,and the simulation of laser ablation is performed.The finite element model results show that the 3D deformation geometry method is proper to modeling the damage effect of high energy laser.And the precorrection can increase the peak power density and improve the efficiency of damage.