2.94μm室温连续Er:YAG激光器的研制

Development of 2.94μm room temperature CW Er:YAG laser technology

研制了一种结构简单的LD端面泵浦2.94μm Er:YAG连续激光器。该激光器采用双端键合YAG端帽方式降低了晶体的端面温度。泵浦源采用小芯径的输出光纤和非球面镜耦合系统,减小了小泵浦光斑在晶体中的发散速度,并提高了泵浦均匀性。当泵浦光波长为969.7 nm时,Er:YAG晶体前段对泵浦光的吸收较弱,因此激光器增益介质前端热聚集效应得到了缓解。通过热像仪在实验中对键合和非键合Er:YAG晶体端面温度进行观测对比,并使用COMSOL软件对激光器热分布进行了模拟分析,证明了上述措施对减小高掺杂Er:YAG晶体热效应的有效性。最终成功实现了155 mW的2.94μm连续激光输出。另外还观测到激光器输出波长随泵浦功率增加的红移现象并对其在能级跃迁层面进行了理论解释。

In this paper,we report a simple structure,room-temperature operation,LD end-pumped 2.94μmEr:YAG continuous wave laser.The laser uses double-ended bonded YAG end caps to reduce the end-surfacetemperature of the crystal.The pump source uses a small core diameter output fiber and an aspheric mirror couplingsystem,which reduces the dispersion rate of small pump spots in the crystal and therefore improves pumpinguniformity.When the pump light wavelength is 969.7 nm,the absorption of pump light in the front section of Er:YAGcrystal is weak,accordingly the thermal aggregation effect of the front end of the laser gain medium is mitigated.Weobserved and compared the temperature of the end faces of bonded and non-bonded Er:YAG crystals with a thermalimaging camera,simulated the thermal distribution using COMSOL software,and proved the effectiveness of theabove measures in reducing the thermal effect of highly doped Er:YAG crystal.We finally succeeded in achieving acontinuous laser output of 2.94μm at 155 mW.We also observed the output wavelength’s red-shift phenomenon withthe pump power increase and explained it theoretically at the energy transfer level.