Tunable Broadband Multi-Wavelength Brillouin-Raman Random Fiber Laser Based on High-Order Raman Pump

Benefiting from the low lasing threshold, Brillouin-Raman fiber lasers are widely used for broadband multi-wavelength lasing radiation. However, the bandwidth of the multi-wavelength Brillouin-Raman fiber lasing becomes narrower when the Brillouin pump (BP) is tuned to longer wavelengths while the Raman pump (RP) wavelength remains fixed. Here, a method for generating tunable broadband multi-wavelength Brillouin-Raman random fiber lasing by utilizing a high-order tunable RP and simultaneously tuning the BP and RP wavelengths is proposed, for the first time. A uniform gain distribution along the passive fiber is enabled by the high-order RP, which facilitates the generation of broadband and flat cascaded Brillouin Stokes lines. As a verification, a tunable broadband multi-wavelength Brillouin-Raman random fiber laser (MWBRRFL) is experimentally presented. The MWBRRFL is enabled by the synergy of high nonlinear gain, Rayleigh scattering, and erbium-doped gain facilitated by dispersion-compensated fiber, standard single-mode fiber, and erbium-doped fiber. The bandwidth and wavelength spacing are 51.05 nm and 20 GHz, respectively. The bandwidth of the tunable MWBRRFL maintains ∼50 nm in the 1508--1583 nm range by simultaneously changing the wavelengths of the RP and BP. The proposed MWBRRFL could serve as a new light source to improve the performance of applications including optical fiber communication, spectral analysis, imaging, optical fiber sensing, etc.