Abstract
We report what is believed to be the first fiber laser operating at 3.55 µm pumped solely by a high-power laser diode at 790 nm. This novel pumping scheme takes advantage of the absorption of 790 nm photons by both thulium and erbium ions to achieve laser emission at 3.55 µm from a monolithic cavity design. The 790 nm pump is first partially used to generate a 1976 nm laser with a thulium-doped silica fiber, and then the residual 790 nm and 1976 nm lasers are used to create a dual-wavelength pumped laser in an erbium-doped fluoride fiber. The single-diode-pumped all-fiber design is made possible by low-loss fluoride fiber splicing and photo-inscribed fiber Bragg gratings. The laser reached a continuous-wave output power of 2.15 W at 3545 nm.