Laser Indoor Simulation Experiments Of Thermal Blooming And Turbulence Effects

When high-power lasers are transmitted in the atmosphere,they are inevitably affected by linear effects such as atmospheric extinction and atmospheric turbulence effects,as well as nonlinear effects such as thermal blooming effect,which not only cause laser intensity attenuation,but also degrade the beam quality and limit high-power laser application performance.It has been shown that the beam distortion caused by turbulence and thermal blooming can be classified as phase influence.The adaptive optical system can correct its distortion.Therefore,it is of great significance to systematically carry out researches on turbulence and thermal blooming transmission in the atmosphere.The high-power laser transmission effects laboratory simulation research method can not only provide experimental conditions for relevant theoretical research,but also overcome the problems involved in laser atmospheric transmission field test,such as many factors problems,poor reproducibility and controllability,difficulty in testing,and high cost.The laboratory simulation method of atmospheric turbulence effect is relatively mature,and the existing high-power thermal blooming experiment simulation mostly adopts the method of high-power laser transmission through strong absorption medium,and the method has high construction cost.The purpose of this paper is to explore a low-cost thermal blooming simulation method that is easy to implement and reliable in simulation.It should also be used in conjunction with turbulence simulation experiments to simulate atmospheric turbulence and thermal blooming effects.In this paper,an experimental simulation method for simulating thermal blooming field distortion is proposed by using the pure phase liquid crystal spatial light modulator?LC-SLM?to load the far field distortion phase pattern obtained by the thermal blooming phase screen method.The Pearson correlation coefficient of the thermal intensity distribution pattern and the simulated light intensity distribution pattern generated by the experimental simulation is no less than 0.72.Experiments verify the effectiveness of the thermal blooming simulation method.LC-SLM with modulation depth of 0-2?and pixel unit of 1024×1280 is used to simulate the thermal distortion of thermal distortion parameter ofN_c 4-50 light field.At present,the research method of thermal blooming effect under atmospheric turbulence is still independent analysis and processing.Based on this principle,this paper designs and builds a laser atmospheric transmission experimental system that considers both turbulence effect and thermal blooming effect,and simultaneously has turbulence and thermal blooming.The beam distortion characteristics of the light after transmission are experimentally studied.The turbulence simulator can simulate the atmospheric turbulence of the atmospheric refractive index structure constantC_n² range3.69?10^-133.22?10^{-1 2} m^-2/3,and the atmospheric coherent length ₀r range 0.034⁰.124m.The distortion beam with the thermal distortion parameterN_c of 4-50 is transmitted in the simulated atmospheric turbulence.The correlation coefficients between the calculated intensity patterns and the simulated intensity patterns are no less than 0.69.The correlations show the two pattern agree well,but are worse than those of the thermal blooming beam.It is due to the effects of turbulence and the increase of transmission distance in the experiment.The above preliminary experiments show that the thermal blooming distortion beam simulation described in this paper and the simultaneous consideration of the turbulence and thermal blooming laser atmospheric transmission system are reliable and easy to use.The experimental simulation system provides important experimental conditions for high-power laser adaptive correction.