热效应是制约固态激光器技术发展的主要障碍之一，也是激光器发展的主要瓶颈。针对一抽运功率为100 W的掺钛蓝宝石激光器设计制造了一套以液氮为冷却工质的低温恒温器，从结构上对恒温器进行了优化设计，用实验的方法验证了该恒温器的热力学性能，用ANSYS软件分析了钛蓝宝石晶体在所设计的热沉条件下的温度分布和应力分布。结果表明该恒温器结构能够满足激光器的要求，且相比于常温冷却，钛蓝宝石激光晶体在液氮温度下温度分布更均匀，热应力更小。

Thermal effects are the main challenge of the technological development in high-power solid-state laser. It is one of the main bottlenecks of lasers. A liquid nitrogen (LN2) cryostat for cooling the Ti:sapphire crystal which is used for a laser with 100 W pump power is presented. The major structure characters of cryostat are introduced. The thermal parameters are identified by experiment. The temperature profile and thermal stress of Ti:sapphire crystal are calculated by ANSYS respectively. The results show that this cryostat satisfies the requirementof laser. The temperature profile of Ti:sapphire crystal cooled by LN2 cryostat is more uniform, and the thermal stress is smaller than that cooled in room temperature.