为了产生大频差可调谐双频激光输出，利用偏振分光棱镜(PBS)的自然分光和起偏作用，将激光谐振腔分成正交的直线腔和直角腔，设计一种激光二极管端面抽运频差可调谐双频Nd∶YAG 激光器。该激光器的两个腔均采用双折射滤光片使1064 nm 振荡激光的p 和s 偏振分量分别以单纵模振荡输出。理论分析双折射滤光片的选模原理和双频激光同时振荡原理，实验研究1064 nm Nd∶YAG 激光单纵模振荡特性和调频特性。实验观察到的1064 nm 双频激光的频差调谐范围为11.4~168.6 GHz，其最大频差达到Nd∶YAG 的荧光线宽。这种大频差可调谐1064 nm 双频Nd∶YAG激光器可广泛应用于激光干涉测量和激光光谱学等领域。

In order to obtain the tunable dual-frequency laser with large frequency difference, a laser diode endpumped dual-frequency Nd∶YAG laser with tunable frequency difference has been designed, using the light splitting and polarizing functions of the polarizing beam splitter (PBS) to form perpendicular straight and right angle standingwave cavities. Both cavities employ birefringent filters acting as laser axial mode selectors. The p-and s-component of 1064 nm laser light can therefore be forced to oscillate simultaneously in single longitudinal mode. The principles of single longitudinal mode selection by birefringent filter and the simultaneous oscillation of the dual-frequency laser have been theoretically analyzed, and the characteristics of Nd∶YAG laser with single longitudinal mode oscillation at 1064 nm and frequency difference tuning have been investigated experimentally. It has been observed experimentally that the frequency difference of the dual-frequency laser at 1064 nm is tunable in a range from 11.4 GHz to 168.6 GHz, the maximum frequency difference has reached the fluorescence line width of Nd∶YAG. Such a dual-frequency Nd∶YAG laser can be used for laser interferometric measurement, laser spectroscopy and other fields.