Feedback intensity adjustable half-open-cavity random fiber laser based on erbium-doped fiber

A half-open cavity random fiber laser with tunable feedback intensity by leveraging strong random feedback between erbium-doped fiber (EDF) gain and Rayleigh scattering-enhanced fiber (RSEF) has been constructed. The laser output characteristics of the established random laser have been measured with 20 m RSEF and 5-km SMF, respectively. Results show that RSEF could be beneficial to the enhancement of spectral purity, linewidth narrowing, and stabilization of output power. Furthermore, the influence of feedback intensity on the output laser properties has also been systematically investigated, with the optimal performance of single-frequency random laser output with an optical signal-to-noise ratio (OSNR) of 55.5 dB, relative intensity noise (RIN) of -100 dB/Hz, and a linewidth of 307 Hz.