Compact single-end pumped Brillouin random fiber laser with enhanced distributed feedback

A compact sub-kilohertz linewidth Brillouin random fiber laser (BRFL) based on a linear cavity scheme with single-end pumping and enhanced distributed Rayleigh feedback from fiber random gratings (FRGs) is proposed and demonstrated. The improved FRGs with low transmission loss make the single-end pumped linear cavity configuration achievable without sacrificing the lasing capability, which contributes to a more compact setup for easy integration and packaging. The enhanced Rayleigh feedback from the FRG enables a high-efficiency random lasing resonance of the Stokes wave via stimulated Brillouin scattering in the lasing cavity. More importantly, the single-end pumped scheme, unlike the previously reported bi-directionally pumped BRFL, significantly alleviates the lasing instabilities and noises induced by the counter-propagating laser beams through the Brillouin-active medium, thus exhibiting lower lasing noises. Single-longitudinal-mode operation of the proposed random laser is realized with a narrow linewidth of similar to 0.97 kHz. (C) 2020 Optical Society of America