高功率固体激光器增益非均匀分布引起的效能亏损效应研究

Efficiency loss induced by non-uniform gain distribution in high power solid state lasers

激光晶体由于吸收了一部分泵浦光能量,产生的热量引起晶体内温度不均匀分布,使晶体内的折射率产生不均匀分布,对振荡光产生相应的相位调制,引起振荡光光场再分布,进而导致振荡光模式发生变化。谐振腔具有滤波作用,谐振腔会过滤掉振荡光中与谐振腔不匹配的模式,引起损耗,用MATLAB模拟晶体内温度场分布,通过计算谐振腔内基模的热致损耗及低阶模转换到高阶模的比例,并研究谐振腔中各阶模式的转换问题,为抑制高阶模并减小损耗提供理论依据。

Heat generated by the absorbed pump light always results in a non-uniform distribution of temperature in the laser crystal, which leads to a non-uniform distribution of refractive index in the crystal. Therefore, a phase modulation can be produced when the oscillating beam passes through the crystal, thus the oscillating light field can be redistributed and deviated from the ideal mode distribution. Because of the filter function of the resonator, the resonator filters out the beam profile that does not match the ideal resonator mode and causes loss. By calculating the thermal loss of the fundamental mode and the conversion ratio of the low-order mode to the high-order mode, the temperature field distribution in the crystal was simulated with MATLAB, the energy interchange between the modes in the resonator was studied, which could provide a theoretical basis for suppressing the high-order mode and reducing mode loss in solid state laser.