Low-Cost High-Efficiency Brillouin Random Fiber Laser Based on Coherent Self-Injection Locking

We realize a narrow-linewidth Brillouin random fiber laser (BRFL) that uses the proposed coherent self-injection locking with a semi-open linear cavity configuration. The proposed laser demonstrates balanced performance, including a low threshold power of 9.22 mW, high laser efficiency of 20%, and exceptional optical signal-to-noise ratio (OSNR) of 67.01 dB. Moreover, the linewidth is compressed from the hundred-kilohertz level to the hundred-hertz level, achieving a 3 dB linewidth of 412 Hz, which corresponds to a 1214 times compression relative to the pump laser. Statistical analyses confirmed that multimode resonances are effectively suppressed, thereby significantly enhancing single-mode stability. Furthermore, frequency noise measurements confirmed significant noise suppression across the entire tested frequency range. These results highlight the potential of coherent self-injection locking for developing highly stable, efficient, and narrow-linewidth BRFLs, making them promising for precision optical applications.