Analysis of far-field characteristics with repetition frequency of TEA CO₂ laser

In order to study the influence of TEA CO2 laser repetition frequency on far-field beam quality, the temperature field and thermal deformation distribution of the mirror were calculated firstly by the finite element analysis of thermodynamics instantaneous method with TEA CO2 laser irradiation of different repetition frequencies. Then, mirror thermal distortion was fitted by Zernike polynomials. Finally, far-field characteristics of different repetition frequencies TEA CO2 laser were obtained by the angular spectrum propagation theory of diffraction. The theory and simulation results show that with the increasing of laser repetition frequency, the mirror temperature and thermal deformation are gradually increasing. After thermal deformation effect, Sr and the average energy density Ed decrease, and parameter gradually increases in the far field. Comparing with 10 Hz, Ed of 300 Hz decreases 40%, peak power in the far field decreases 43% and beam waist broadens 60%. When the laser repetition frequency is greater than 100 Hz,due to the appearance of peaks and valleys on the mirror, the far-field beam quality decreases significantly. The results of this paper can provide the reference to TEA CO2 laser launch system.