【摘要】 本文首先从二次谐波产生（ＳＨＧ）过程中的一对耦合波方程出发，在理论上得到了当基波光以接近相位匹配的角度穿过倍频晶体时会产生自聚焦效应，并用类比方法得到了ＢＢＯ晶体相应的非线性折射率系数．在实验上，据我们所知首次将ＢＢＯ倍频晶体作为独立自聚焦元件用到了钛宝石激光器中，获得了一台较腔内不加晶体时的锁模阈值明显减小、锁模稳定性明显提高且具有自启动能力的自锁模钛宝石激光器．更多还原

【Abstract】 In theory,from the coupled-wave equations governing SHG we have obtained that the effectof self-focusing can occur when the fundamental wave propagates through a BBO crystal close to thephase-matching angle. In experiments ,by use of BBO crystal as an additional intracavity self-focusingelement in a self-mode-locked Ti:sapphire laser,we have observed that the pump power threshold andstability for self-mode-locking can be significantly improved,and that the mode-locking can be self-starting.更多还原