New schemes and regimes of CW and pulsed Raman fiber lasers

A review of recent results on new schemes and regimes of Raman fiber lasers (RFL) is presented. The key feature of RFLs is generation in new wavelength ranges, which are not covered by existing fiber lasers based on rare-earth doped active fibers. New high-brightness 9хх nm all-fiber source based on directly diode pumped passive GRIN multimode fiber with in-core fiber Bragg gratings (FBGs) enables high-efficiency Raman generation of high-quality (M2≤2.6) beam at powers up to ~100 W with further scaling capabilities. Mirrorless scheme based on Rayleigh-backscattering random distributed feedback (RDFB) in a singlemode polarization-maintaining (PM) fiber provides ultimate pump-to-Stokes conversion efficiency for the first order as well as cascaded generation of higher orders in 1-2 μm range. Single-frequency Raman lasing in a short (~10 m) PM fiber with RDFB based on random FBG array has been also demonstrated. Pulsed operation of RFL at active Q-switching and mode-locking in passive fibers is realized with pulse energies and durations of up to 30 μJ and ~50 ps, correspondingly. New regime of Raman dissipative solitons (of the first and second Stokes orders) synchronously generated in a common or external resonant cavity and their nonlinear mixing in PCF provide generation of