对二极管激光器端面抽运的准三能级自倍频激光系统进行了详细的理论研究。首先,利用准三能级的速率方程和缓变包络近似,从Maxwell方程出发,建立了准三能级自倍频激光器空间耦合波方程。然后结合典型二极管激光器抽运Yb:YAB激光器的相关参数,用计算机模拟了该激光系统的数值解,理论结果显示自倍频光和基频光受晶体的温度影响很大,当晶体温度升高时,激光输出迅速降低;在有效倍频长度内,分别存在不同的最佳晶体长度使自倍频光和基频光输出最大;同时也得到了自倍频光与基频光强度成二次方变化的普遍倍频规律。最后利用M2因子对自倍频光和基频光的相对强度受抽运光光束质量的影响作了定量分析。

Based on Maxwell′s equation, spatially coupling wave equation of self-frequency-doubled (SFD) lasers with quasi-there energy levels was derived by virtue of the rate equation of quasi-there energy levels system and the slowly varying envelop approximation, with the situation that the media end pumped. Characterization of SFD Yb:YAB [YAl3(BO3)4] lasers typically pumped by laser diode (LD) was numerically simulated. The simulation showed that intensity of SFD harmonic increased quadratically with the increase of intensity of fundamental harmonic, while intensity of SFD harmonic and fundamental harmonic decreased sharply with the increase of temperature. Within the effective doubled-frequency length, there are different optimal crystal lengths for fundamental and SFD harmonic output being maximum, respectively. Influence of quality of pumping beam on the fundamental and SFD harmonic output of laser was quantificationally evaluated by means of M2 factor.