Low-Threshold, High-Efficiency Random Fiber Laser With Linear Output

In this letter, we numerically study and experimentally achieve a low-threshold, high-efficiency random fiber laser, featuring a linear output as well. The lasing cavity incorporates a section of standard single-mode fiber and a band-selective point reflector placed at the far end of the fiber. The numerical result indicates that most energy is further pushed toward the pump side comparing with the open cavity scheme, producing a high-efficiency output. Then, we analyze the dependence of threshold and slope efficiency on cavity length and pumping wavelength. Most importantly, shorter cavity length would yield higher efficiency, and for different pumping wavelengths, there will be different cavity lengths corresponding to the lowest lasing threshold. Finally, we deliberately choose the parameters and experimentally achieve an 1145-nm random fiber laser with 7.13-W output and >90% slope efficiency (with 10-W pump), while the slope efficiency is almost constant above the 2-W lasing threshold. This letter provides a comprehensive guideline for designing such random fiber lasers with tailored performance.