Spectral characteristics of CH4-filled hollow-core fiber Raman laser amplifier

A 1.5 μm tunable CW single-frequency seed laser is injected into the methane-filled negative curvature hollow-core fiber, and then amplified by stimulated Raman scattering of methane molecule. The Stokes linewidth is measured at the output using a scanning Fabry-Perot interferometer. When the wavelength of the seed laser is tuned to the Stokes transition and the polarization direction of the seed laser and the pump laser is nonorthogonal, the introduction of the seed laser significantly narrows the Stokes linewidth. This paper paves a feasible way to obtain high power· narrow linewidth laser output in gas filled hollow-core fiber by stimulated Raman scattering.