端抽运Yb^(3+):YVO_4激光准三能级理论模型研究

The modeling of end pumping Yb^(3+) :YVO_4 quasi-three-level laser

立足于Yb离子能级结构、谐振腔增益损耗和布居数分配情况,利用爱因斯坦辐射理论和速率方程理论,建立了适合Yb3+离子激光的准三能级理论模型.该模型引入有效腔长增益贡献因子对腔内光强进行了从头计算,获得了阈值方程.利用此模型与Yb激光的实验结果相比较,发现有效腔长对增益的贡献可以改变腔内损耗和粒子数反转的概率,也继而影响激光阈值和输出功率效率.应用于LD端抽运Yb3+:YVO4激光实验中,在971nmLD抽运,有效晶体长度L=1mm,输出镜透过率对激光波长1016nm为1%条件下,获得阈值为1.1W;有效晶体长度L=2mm,输出镜透过率为10%条件下,阈值获得为3.9W.

In a Yb3＋ laser, the two-energy level structure is close to the quasi-three-level model, but different from that for the Nd and Tm lasers, so it is necessary to investigate the quasi-three-level modeling that will be applied to the Yb3＋ laser. Based on the energy level structure, cavity gain and loss as well as population distribution, we present the modeling. Introducing an effective cavity length factor, the laser intensity is calculated and the threshold is obtained. Comparison with the experiments, indicates that the effective cavity length ratio changes the fractional population function and loss, which would influence the threshold and output in turn. Applied to investigate the laser property in the process of end pumping Yb3＋ ：YVO4 laser, we get the threshold being 1.1 W, corresponding to the L = 1 mm and T = 1%; whereas the threshold is 3.9 W, corresponding to the L = 2 mm and T = 10%.