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针对2kW射频板条CO2激光器离轴负支非稳波导混合腔的近场分布存在较多高空间频率分量,导致聚焦后会产生不可忽略的旁瓣,无法直接应用于激光加工的问题,对谐振腔的近场分布使用特征向量法和矩形波导的解析表达式进行了数值模拟和实验研究。并结合Collins公式研究了输出光束整形过程中光场分布的变化和整形系统中空间滤波器的优化设计。理论和实验结果表明:激光器输出光束在整形前为有较多高空间频率振荡的长条形的简单象散光束。通过带空间滤波器的整形系统消除旁瓣,并将初始的长条形的简单象散光束整形成近圆形、近基模高斯分布的光束。整形后的光束非稳方向的光束质量因子M2为1.1,波导方向M2为1.08。
The near-field distribution of 2kW RF slab CO2 laser with off-axis negative branch unsteady waveguide has many high spatial frequency components, resulting in non-negligible side lobes after focusing, which can not be directly applied to the problem of laser processing. The near-field distribution of the cavity is numerically simulated and experimentally studied using the eigenvector method and the analytical expression of a rectangular waveguide. Combining the Collins formula, the change of the light field distribution in the output beam shaping process and the optimization design of the spatial filter in the shaping system are studied. Theoretical and experimental results show that the laser output beam is a strip-shaped simple astigmatic beam with more high spatial frequency oscillation before shaping. The sidelobes are eliminated by a shaping system with a spatial filter, and the initial, simple, shaped astigmatic beam is shaped into a nearly circular, near-fundamental, Gaussian beam. The beam quality factor M2 in the unsteady direction of the shaped beam is 1.1 and the waveguide direction M2 is 1.08.