Thermal effect of high-power laser propagation in complex channels and its mitigation

We investigate the channel thermal effect resulting from the gas thermal blooming effect and mirror thermal deformation on the beam quality, and we propose a mitigation measure for blowing purge gases. Without gas blowing, the gas thermal blooming effect opposes the influence of mirror thermal deformation on the beam phase, resulting in significant phase distortion and offset. Noticeable distortion and divergence of the laser spot was also observed. After blowing purge gases, the beam phase was primarily determined by the mirror thermal deformation. Simultaneously, the mean-squared beam width decreased uniformly, improving the symmetry and energy concentration of the laser spot. However, the laser spot tended to stabilize when the gas velocity exceeded a certain threshold.