为了实现小型化、高功率、高效率连续2 μm激光输出,采用中心波长792 nm激光二极管(LD)抽运双掺杂Tm,Ho∶YLF晶体,将晶体封装在装有350 mL液氮的杜瓦装置中,使其工作在77 K温度条件下。光纤耦合激光二极管出纤功率14.8 W,数值孔径0.3,芯径400 μm。激光二极管端面抽运Tm,Ho∶YLF激光器,产生2.05 μm线偏振连续激光输出,最大功率5.2 W。由于Tm3+离子能级间的交叉弛豫效应导致的高抽运量子效率,实验获得的光-光转换效率为35%,斜度效率达到40%。采用双端面抽运结构,两个激光二极管注入功率29.6 W时,Tm,Ho∶YLF激光器输出功率达10.2 W,相当于光-光转换效率33%,斜度效率36%。

In this paper, a high power of cryogenic Tm(8 at.-%),Ho(1.4 at.-%)∶YLF end-pumped by a fiber-coupled laser diode (LD) with number aperture of 0.3, core diameter of 0.4 mm, and central wavelength of 792 nm at 20 ℃ temperature is reported. The highest continuous-wave (CW) power of 5.2 W at 2.05 μm is achieved under pump power of 14.8 W, corresponding to optical-optical conversion efficiency of 35%, and the slope efficiency is greater than 40%. The threshold power is only about 0.48 W because of the long lifetime, large effective emission cross section, and low reabsorption loss in Tm,Ho∶YLF crystal. Under pumping power of 29.6 W with dual-end pumping configuration, the highest CW power of 10.2 W at 2.051 μm is attained, corresponding to optical-optical conversion efficiency of 33%, and the slope efficiency is greater than 36%.