The thermal properties of photonic crystal fiber (PCF) laser with 18 circularly distributed cores are investigated by using full-vector finite element method (FEM). The results show that the 18-core PCF has a more effective thermal dispersion construction compared with the single core PCF and 19-core PCF. In addition, the temperature distribution of 18-core PCF laser with different thermal loads is simulated. The results show that the core temperature approaches the fiber drawing value of 1800 K approximately when the thermal load is above 80 W/m which corresponds to the pumping power of 600 W approximately, while the coating temperature approaches the damage value of about 550 K when the thermal load is above 15 W/m which corresponds to the pumping power of 110 W approximately. Therefore the fiber cooling is necessary to achieve power scaling. Compared with other different cooling systems, the copper cooling scheme is found to be an effective method to reduce the thermal effects.

针对光纤的泵浦耦合问题，对由两片非球面透镜组成的接近1∶1光纤间空间耦合器进行了计算和实验验证.利用高斯光束的变化规律对光路进行了分析研究，并根据二极管输出光相干性不好的特点，对非球面透镜进行了光路追迹的模拟计算.研究发现，在泵浦光波长等因素发生变化时，利用椭球面透镜组成的耦合系统较双曲面透镜有更高的稳定性.实验中选用符合计算结果要求的非球面透镜组成耦合装置,利用一台二极管激光器(尾纤输出端面直径约200 μm，N.A.约0.2)泵浦一段芯径约200 μm(N.A.约0.42)的多模光纤，耦合装置的透过率约95%，在光纤端面有反射的条件下约90%的泵浦光耦合进光纤.