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由于2 mm激光处于人眼安全区和大气的弱吸收带,因此掺铥光纤激光器受到了广泛关注。比较了掺铥双包层光纤在激光二极管(LD)抽运时后端分别采用平面镜和凹面镜下激光器输出功率特性。实验和理论表明,由于光纤端面和平面反射镜之间存在着间隙、倾斜以及光纤端面存在缺陷等因素,使得激光腔的损耗增大,激光器输出性能受到严重影响。根据波动理论分析了光纤后端面分别采用平面反射镜和凹面反射镜下谐振腔插入损耗特性,理论表明采用凹面反射镜时谐振腔损耗要比采用平面反射镜时小。光纤后端的腔镜采用凹面镜时,获得最大输出功率为22 W,对应的中心波长为1998.6 nm,相对于入射抽运光功率的斜率效率为43%的激光输出。相比采用平-平腔的激光器其斜率效率提高了10%,镜面承受的热损伤得到大幅缓解。
Due to the 2 mm laser in the human eye safe area and the weak absorption band of the atmosphere, doped 铥 fiber laser has been widely concerned. The output characteristics of lasers with flat mirrors and concave mirrors were compared at the back end of doped double clad fiber with laser diode (LD) pumping. Experiments and theoretical results show that laser cavity loss and laser output performance are severely affected by the existence of gaps and tilts between the end face of the fiber and the plane mirror and defects of the fiber end face. According to the wave theory, the insertion loss characteristics of the resonator under the plane mirrors and the concave mirrors are respectively analyzed. The theory shows that the cavity loss is smaller than that of the plane mirrors when using concave mirrors. With a concave mirror at the rear end of the fiber, a laser output with a maximum output power of 22 W and a corresponding center wavelength of 1998.6 nm with a slope efficiency of 43% with respect to the incident pump power was obtained. The slope efficiency is increased by 10% compared to a flat-cavity laser, and the thermal damage on the mirror surface is greatly reduced.