A Study Of Simulation Calculation For Laser Beam Propagation Through Atmosphere

This paper based on the theory of turbulence and thermal blooming. The multi-phase screen model of laser beam through atmosphere has been build. The analysis of the effect of turbulence and thermal blooming upon the laser beam has been done. The relation between turbulence and thermal blooming when the Fried number bigger than the size of laser beam has been given. The laser beam propagation with the turbulence and thermal blooming has been study. Furthermore, a program has been made with MATLAB. The simulation calculations has been given and compared with the result given by scaling law of high power laser. The paper including three parts:On the basis of multiple-phase-screen model, combining spectrum inversion method an fast Fourier transform, This thesis simulate the laser atmospheric transmission characteristic under the influence of turbulence. The conclusion is that the facular size increases with the increase of the transmission distance of laser and that the spot fragmentation phenomenon is more serious with the increase of turbulence intensity.On the basis of multiple-phase-screen model, combining spectrum inversion method an fast Fourier transform, This thesis calculated the transmission of continuous laser beam with the existence of thermal-blooming. The simulation of laser transmission consider the situation of different initial beam intensity, different transmission distances and different transverse wind speed. The conclusion is that with the increase of distance and energy, crescent-shaped distribution caused by thermal blooming is more obvious. What’s more, wind speed can cause the inhibition of thermal blooming effect, in other words,wind speed increases, thermal blooming effect drop off.The third part give the simulation calculations of laser propagation with the effect of turbulence and thermal blooming. When the Fried number bigger than the size of laser beam, the effect of turbulence and thermal blooming would work independently. In this case, with the theory mentioned in the second and the first part, the simulation calculations of laser beam transmission in atmosphere with differ distance, differ energy, differ wind speed have been done. The results show that the spot with the feature of turbulence and thermal blooming. The distribution of the spot is more uniform with the increase of turbulence intensity, and the crescent-shaped distribution of the spot has disappeared. Compared with the result given by the scaling law of high power laser, the outcome are in good agreement. Indicated that the way of simulation given by this paper is practical significance.