Role of the mirror's reflectivity in forward-pumped random fiber laser.

In this paper, we thoroughly analyze the role of the point reflector's reflectivity in the performance of forward-pumped random fiber laser, in both the long- and short-cavity cases. The results show that the power performance is sensitive to the small reflection added on the pump side of the fiber end, whereas both the power distribution and threshold tend to be stable when the reflectivity reaches a relatively high level (>0.4). Moreover, for the short cavity case (e.g. 500m), the maximum achievable 1st-oder random lasing output can even increase when the reflectivity decreases from 0.9 to 0.01, due to the different lasing power distributions with different reflectivity values. This work reveals a new and unique property of random fiber lasers and provides insights into their design for the applications such as distributed amplification and high power sources.