Two-dimensional-simulation of thermal blooming effects in ring pattern laser beams

Thermal blooming is a major effect in high power laser beams transmitting through gaseous medium as well as the atmosphere. Due to this effect, the beam pattern is deformed through the propagation path. In this work, a ring pattern beam from a high-power CO2 laser with an unstable resonator is evaluated when propagating through a high-pressure CO2 gas, and the results are compared with those of the Gaussian beam. The results show that unlike the initial Gaussian beam from which a ring pattern formed when propagating through an absorbing medium, for the initial ring pattern beam, in the absence of the gas flow, a symmetrical two-fold pattern is formed due to the blooming effect. The results also show that such symmetry can be deformed in the presence of gas flow.