提出了一种新型支撑结构以解决大口径晶体重力凹陷作用引起的三倍频转换效率损失问题。有限元分析结果表明：当KDP晶体及支撑结构均为理想平面时，重力作用导致的三倍频转换效率的损失量几乎为0。同时，针对不同倾斜角度下的接触面加工误差对三倍频转换效率的影响进行了大量的数值模拟。计算结果表明：采用新型支撑结构，不同倾斜角度对三倍频转换效率的影响基本相同；支撑结构表面存在随机加工误差对三倍频转换效率的影响程度较小；而当支撑结构存在凸形或凹形加工误差时，加工误差容许值必须控制在5 μm范围内以实现高效三倍频输出。

A mounting configuration is presented to solve the loss of the third harmonic generation (THG) efficiency due to the gravitational effects. The analysis result of finite element model shows that the loss of the THG efficiency is nearly absent due to the gravitational effects when the original surface profile of the KDP crystals and mounting configuration is an ideal plane. Meanwhile, numerical simulation calculations are performed to analyze the influence of fabrication errors on the THG efficiency. Furthermore, the machining requirements of the peripheral milling have been discussed. The loss of the THG efficiency is nearly same under the different departure angles. The mounting configuration with the random error is acceptable, but the convex error and concave error should be controlled below 5 μm to realize efficient third harmonic output.