为了获得大频差双频激光输出, 设计了一种由偏振分光棱镜和半波片组成的新型双折射滤光片作为激光纵模选择元件。将这种新型双折射滤光片置于激光二极管(LD)抽运Nd:YAG激光器的谐振腔内, 实现了单纵模激光振荡。绕激光腔轴旋转半波片以改变波片快轴与偏振分光棱镜偏振面之间的夹角, 发现单纵模激光输出功率发生周期性变化, 变化周期约为π/2。设计并实验研究了一种LD抽运双腔大频差双频Nd:YAG激光器, 其两个驻波谐振腔(即直线腔和直角腔)共用相同的激光介质和纵模选择元件, 1064 nm激光p分量和s分量分别在直线腔和直角腔内同时以单纵模振荡, 改变每一谐振腔的长度可以调谐腔内单纵模激光的谐振频率, 从而实现双频激光频差调谐。实验观察到1064 nm正交线偏振双频激光的频差在27～113.4 GHz范围内可调谐。

In order to obtain the output of dual-frequency laser with large frequency difference, a new birefringent filter consisting of a polarizing beam splitter and a half wave-plate has been designed as a laser longitudinal mode selector. When the birefringent filter is included in a laser-diode(LD)-pumped Nd:YAG laser cavity, the laser is enforced to oscillate in single longitudinal mode. When the angle between the fast axis of the half wave-plate and the polarizing plane of the polarizing beam splitter is changed by rotating the half wave-plate around the laser cavity axis, the output power of the single axial mode laser varies periodically with a period of approximately π/2. A LD-pumped two-cavity dual-frequency Nd:YAG laser with large frequency difference has been designed and experimentally investigated, which has both straight and right angle standing-wave cavities sharing the same gain medium and the longitudinal mode selector. The p-and s-component of 1064 nm laser light oscillate simultaneously in single longitudinal mode in the straight and right angle cavities, respectively. The resonant frequency of the single longitudinal mode oscillated in each resonant cavity can be tuned by changing each cavity-length so that the frequency difference of the dual-frequency laser is tuned. It has been observed experimentally that the frequency difference of the orthogonally and linearly polarized dual-frequency laser at 1064 nm is tunable in a range from 27 to 113.4 GHz.