中文摘要：

提出了一种改良的非稳腔热透镜测量方法，采用此方法对Nd：YAG连续激光器临界稳定点的输出功率进行测量，计算得到Nd：YAG晶体连续工作模式下的有效热透镜焦距，同时对主动调Q Nd：YAG激光器进行实验，采用改良非稳腔方法测量了主动调Q Nd：YAG激光器的热透镜的焦距。连续和调Q工作模式下的热透镜焦距实验结果有较好的一致性。文中对固体激光器的热透镜焦距进行了理论计算，理论计算结果与实验结果在误差范围内能较好地吻合，证明了文中提出的热透镜改良测量方法的有效性和可靠性。

英文摘要：

A simple improved method using resonator critical unstable point is applied to measure the thermal lens focal length of a LD pumped Nd：YAG laser. By measuring the output power of the critical stable point, we can calculate the effective average thermal lens focal length of Nd：YAG lasers under CW and Q-switched working modes, and the thermal lens focal lengths of Nd：YAG crystals are calculated theoretically. The experimental results are in a good agreement with the theoretical ones. The method of applying the condition of critical stable point of resonant cavity is relatively simple and practical. So the effectiveness and reliability of thermal lens improved measurement method is proved.