腔内波片产生的Nd∶YAG激光纵模分裂规律研究

Study of Nd∶YAG laser longitudinal mode splitting caused by intracavity wave plates

简要介绍了激光纵模分裂的基本原理，研究了腔内含有1个和2个1/4波片时产生Nd∶YAG激光纵模分裂的规律。实验结果表明：在1064nm Nd∶YAG激光的腔内放置一个1/4波片时，每一激光纵模分裂为2个正交的线偏振模，在波片表面垂直于激光光线的条件下，纵模分裂量（即频率差或波长差）恰好等于激光纵模间隔的一半；当在Nd∶YAG激光腔内沿垂直光线方向平行放置2个1/4波片时，也能产生纵模分裂现象，其纵模分裂量取决于2波片快（慢）轴之间的夹角。在0°-90°范围内调节角度，可使纵模分裂量在一个激光纵模间隔内线性调谐。实验结果与理论分析相吻合。

The basic principle of the laser longitudinal mode splitting is introduced briefly, and the Nd ： YAG laser longitudinal mode splitting produced by placing one and two quarter-wave plates in the cavity of a Nd ： YAG laser is investigated experimentally. The results show that each longitudinal mode is split into two orthogonally and linearly polarized modes, and the splitting magnitude （i. e. , frequency difference or wavelength difference） is just equal to one half of the laser longitudinal mode interval if the end surface of the quarter-wave plate is perpendicular to the laser beam when a quarter-wave plate is placed in the cavity of Nd ： YAG laser at 1 064 nm. The mode splitting phenomenon can also take place when the Nd ： YAG laser cavity contains two pieces of parallel placed quarter-wave plates along the direct/on normal to the laser beam, and its mode splitting magnitude is dependent on the angle between the fast （or slow） axes of both quarter-wave plates. The magnitude can be linearly tuned in one longitudinal mode interval when the angle is adjusted between 0 to 90 degrees. The results obtained experimentally agree with those of the theoretical analysis quite well.