An LD-pumped Raman fiber laser operating below 1 μm

A CW Raman fiber laser (RFL) operating below 1 μm with direct pumping by a high-power multimode laser diode at 938 nm has been demonstrated for the first time. The laser cavity is formed by a normally cleaved fiber end and a highly reflective fiber Bragg grating (FBG) inscribed at the opposite end of a 4.5 km long multimode graded-index fiber. Low-index transverse modes are generated at the first Stokes wavelength of ∼980 nm with an output power of ∼3 W, while the second Stokes wave at 1025 nm also starts to be generated, thus limiting the 980 nm output.