为了产生频差可调谐1 064 nm双频激光输出, 设计了一种扭转模结构双腔双频Nd∶YAG激光器, 其两个驻波谐振腔共用相同的Nd∶YAG增益介质, 以扭转模结构消弱增益空间烧孔效应, 使Nd∶YAG激光器的两个驻波腔均以单纵模振荡, 从而获得正交线偏振1 064 nm双频激光输出.理论分析了扭转模结构激光单纵模选择原理和双频激光同时振荡原理, 实验研究了双频激光振荡特性和频差调谐特性.研究结果表明：双频Nd∶YAG激光器的两个谐振腔能够同时以线偏振单纵模稳定振荡输出, 其频差大小可随激光腔长的改变而调谐, 频差调谐范围可达1个纵模间隔, 实验观察到的频差调谐范围为0.3 GHz～3 GHz.

In order to produce the dual-frequency laser with tunable frequency-difference at 1 064 nm, a two-cavity dual-frequency Nd∶YAG laser was designed using a twisted-mode configuration, the two standing-wave cavities of which share the same gain medium Nd∶YAG, and the twisted-mode configuration reduced or even eliminated the spatial hole-burning effect of gain so that the single longitudinal mode can be oscillated in both standing-wave cavities of the Nd∶YAG laser, thus the orthogonally and linearly polarized dual-frequency laser at 1 064 nm was obtained. The principles of both single longitudinal mode selection of the twisted-mode configuration and the simultaneous oscillation of the dual-frequency laser were theoretically analyzed, and the characteristics of dual-frequency laser oscillation and frequency difference tuning were investigated experimentally. The experimental results show that both cavities of the Nd∶YAG laser can steadily oscillate in linearly polarized single longitudinal mode, and the frequency-difference can be tuned up to one longitudinal mode interval by changing the cavity length, the frequency-difference tuning range is 0.3 GHz to 3 GHz.