热应力双折射产生的热退偏是限制Nd:YAG激光器线偏振输出功率的重要因素，相比于传统[111]切割方向Nd:YAG晶体，[100]切割方向Nd:YAG晶体的热退偏与振荡光偏振方向有关，通过寻找合适的偏振方向，能够显著提高[100]切割方向Nd:YAG激光器的线偏振输出功率。采用半导体端面抽运[111]和[100]切割方向的Nd:YAG晶体棒，使用Cr4+:YAG晶体作为被动调Q晶体，进行被动调Q对比实验研究。实验结果表明，相比于传统的[111]切割方向Nd:YAG晶体棒，采用半导体抽运[100]切割方向Nd:YAG晶体棒进行被动调Q，能够获得稳定、高消光比的线偏振光激光输出，输出激光消光比为5001，稳定度高于96.5%。

Thermal depolarization caused by birefringence is a major factor that limits the output power of linearly polarized Nd:YAG laser. Compared with conventional [111]- cut Nd:YAG rod, the thermal depolarization depends on the polarization direction for the [100]- cut Nd:YAG rod. The linearly polarized output power can be improved by suitable modification of the polarization direction of oscillate laser. The [111]- and [100]- cut Nd:YAG rods are used as the gain medium and the Cr4+:YAG crystal is used as the saturable absorber for passively Q-switched laser. The experiment demonstrates that in comparison with conventional [111]- cut Nd:YAG rod, highly stabled output with high extinction is achieved by using the [100]- cut Nd:YAG rod as the laser crystal. The extinction ratio is 5001 and polarized output stability is higher than 96.5%.