激光晶体侧面接触热导对波前畸变的影响

Influence of thermal contact conductance on the side-face of the crystal rod on wavefront distortion in the solid-state laser

对于采用圆棒状工作物质的二极管端面抽运固体激光器,其晶体棒由两块金属热沉夹持散热,晶体棒侧面受到非轴对称的装配压力使得晶体棒与热沉间接触热导呈非轴对称分布,进而影响晶体棒温度及出射光波前的空间分布.在已有的截断高斯模型和塑性形变模型基础之上,建立了晶体棒与热沉间接触热导模型.对高斯型热耗分布,采用有限元法得到了无热界面物质时,不同装配压力下晶体棒端面温度和波前畸变随半径和方向角的变化,并与采用铟箔作为热界面物质时的结果进行了比较.模拟结果表明:无热界面物质时,在同一半径上,晶体棒端面温度、波前畸变在晶体棒侧面与热沉凹槽底部接触方向最小,在两块热沉接触面方向最大;增大装配压力,晶体棒端面温度整体降低,波前畸变在圆周方向趋于均匀.使用铟箔作为热界面物质时,晶体棒端面温度及波前畸变一致减小,且呈轴对称分布.

For the LD end-pumped solid-state laser working with round-rod material,the crystal rod is held and cooled by the metal heat sinks.The non-axisymmetric assembly pressure on the side-face of the crystal rod makes the thermal contact conductance between the crystal and the heat-sink non-axisymmetric,which affects the spatial distribution of the temperature inside the crystal rod and the spatial distribution of wavefront.Based on the truncated-Gaussian model and the plastic-deformation model,the model of the thermal contact conductance is established.For the Gaussian heat consumption,the changes of the end-face temperature of the crystal and the wavefront distortion with the radius and the direction angle under different assembly forces are obtained,and the results are compared with those of the case when using the indium foil as thermal interface material.The results show that in the case of the same radius the end-face temperature and the wavefront distortion reach the minimum in the direction of bottom of the heat-sink groove,and reach the maximum in the direction of the contact area of the heat-sink couple.With the increasing assembly force,the end-face temperature reduces overall,and the wavefront distortion gets more uniform.With the indium foil as thermal interface material,the end-face temperature and the wavefront distortion decrease overall.And the the spatial distribution of the temperature of the crystal rod and the wavefront distortion is axisymmetric.