Generation of broadband continuous-wave supercontinuum Raman lasing in a fiber ring cavity

Build-up process of the broadband continuous-wave supercontinuum Raman lasing (CWSCRL) in a fiber ring cavity is reconstructed theoretically through simulation based on the generalized nonlinear Schrodinger equations in the spectral domain. The physical mechanism of the CWSCRL is revealed as a combined effect of light amplification by stimulated Raman scattering and spectral broadening by four wave mixing in the view of the spectral domain. Detailed analysis as well as experimental confirmation shows that broad and flat spectrum can be achieved mainly by assigning the pumping wavelengths so that the first Raman Stokes wavelengths occur at both sides of the zero dispersion wavelength of the highly nonlinear dispersion-shifted fiber in the ring cavity, while optimization in pump power also matters. Different time structures of the Raman lasing are determined by the dispersion at the first-order Raman Stokes light wavelengths.