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建立了封闭水平管道中激光传输热效应物理模型,详细研究了降低气体压强对光束质量变化的影响,辨别了热传导、浮力对流传热机制的转换时间与光束质量、光斑质心漂移转换时间的关系;数值模拟了气体吸收不同激光能量,在不同压强下的温度分布、附加相差和远场光束质量、光斑质心漂移的变化。结果表明,气体温度分布与气体热光系数两种因素共同决定远场光束质量变化的大小,而光束质量转换时间与两种传热机制转换时间一致,光斑质心漂移转换时间略有滞后;降低管道中气体压强,可较大地改善远场光束质量。
The physical model of thermal effect of laser transmission in a closed horizontal pipe was established. The effect of reducing the gas pressure on the beam quality was studied in detail. The relationship between the conversion time of the heat conduction and the buoyancy convection heat transfer mechanism and the beam quality and the transition time of the center of mass and the center of mass of the light spot were analyzed. The variations of gas absorption of different laser energy, temperature distribution under different pressures, additional phase difference and beam quality in far field, and mass center drift of light spot were simulated. The results show that the gas temperature distribution and the gas thermo-optic coefficient jointly determine the quality of the far-field beam. The conversion time of the beam mass is consistent with the conversion time of the two heat transfer mechanisms, In the gas pressure, can greatly improve the far-field beam quality.