Numerical simulation of the thermal effect in a beam control system

A four-dimension simulation code is developed,which enables us to study the thermal effect of high-power lasers propagating through a beam control system.As illustrated examples,the thermal effects of high-power lasers with initial Gaussian and flat-topped profiles in passage through the beam control system on the beam quality in the far field characterized by the Strehl ratio,the focussiablity(i.e.,radius of the encircled 86.5% power),astigmatism parameter and shift of the beam gravity are studied.It is shown that the beam quality in the far field depends on the initial field distribution,and is degraded with increasing emissive power.