Modeling and optimization of cascaded lasing in a holmium doped fluoride fiber laser with efficient output at 3.92 µm
Jianing Cao, Wei Chen, Hongrong Zhou, Wenshu Liu, Chencheng Shang, Huimin Yue, Yong Liu
Abstract
In this paper, we investigate the output performance of a continuous-wave Ho 3+ -doped fluoride fiber laser operating at 3.92 µm from the 5 I 5 → 5 I 6 transition of Ho 3+ using numerical simulation. A double-clad Ho 3+ -doped fluoroindate fiber with a doping concentration of 10.0 mol.% is assumed, with direct pumping at 888 nm. We propose simultaneous lasing on the 5 I 6 → 5 I 7 transition to enhance the slope efficiency while reducing the threshold and heat accumulation. Simulation results indicate that a slope efficiency of 17% and a threshold of 2.5 W can be obtained using a 9 cm-long fiber. Moreover, with the heat accumulation reduced by >40%, watt level laser output can be achieved in this cascade system at room temperature without the gain fiber being damaged by heat accumulation. The theoretical maximum output power of 1.27 W is 6 times higher than the highest reported value (197 mW), which is limited by the fiber damage due to excess heat load.