采用堆叠法制作了纤芯直径为20 μm的Nd3+离子掺杂磷酸盐玻璃D形双包层光纤，采用793 nm半导体激光作为抽运源，测定并分析其光纤激光性能和斜率效率，光纤的最大输出功率为2.52 W，斜率效率为41.5%。采用同样的办法进一步制作了六角形、偏心形和圆形内包层结构的光纤，对比研究了内包层结构对光纤输出性能的影响。结果显示相比于其他内包层结构的光纤，D形内包层结构光纤对抽运光的吸收效率更高，有助于光纤激光性能的提高。

D-shaped double cladding (DC) Nd3+-doped phosphate glass fiber with the core diameter of 20 μm is fabricated by the stacking technique and pumped by a commercial 793 nm laser diode. The maximum output power of 2.52 W at 1053 nm is generated, with the slope efficiency of 41.5% respects to the absorbed pump power. To investigate the effect of inner cladding on fiber laser performance, hexagonal, eccentric and circular DC fibers are fabricated and analyzed with the same procedure as the D-shaped fiber. The results show that among all the DC fibers with different inner claddings, the D-shaped fiber has the highest pumping power absorption, which is beneficial to improve the fiber laser performance.