在端抽运圆棒二极管抽运固体激光器(DPL)中，引入偏离因子来描述抽运光轴线和激光晶体间的同轴程度；并将偏离因子对模式增益和光束质量的影响做了理论分析和模拟，并以光纤耦合半导体激光器端面抽运圆棒Nd:YAG固体激光器进行了相应实验。理论与实验结果表明，偏离因子越小，则低阶模模式增益越大，在模式竞争中占据优势，输出激光的光束质量越好。要获得高增益和光束质量较好的低阶模输出，除了保证恰当的谐振腔结构外，控制抽运光与激光晶体同轴程度也是一个重要的手段。

In laser diode end-pumping solid-state lasers, the departure gene is introduced to describe the coaxial degree betweem the pumping light and the columniform laser crystal. The effects of the departure gene on the gain efficient of the oscillating modes and output beam quality are analyzed in theory, and the corresponding experiment is done with the fiber coupling diode lasers end-pumping Nd:YAG lasers. The results of the theory are in accordance with that of experiment: the departure gene is smaller, the gain of lower order mode becomes higher and the output beam quality changes better. Therefore, in order to obtain the lower order mode output with higher gain and better beam quality, control the coaxial degree between the pumping light and laser crystal is an important measure besides holding proper resonat cavity.