Optical spectra of fiber lasers operating at two microns

Abstract This letter compares the optical spectra of holmium- and thulium-doped silica fiber lasers operating in the continuous-wave regime with an output power of about 10 W. The lasers are based on commercial gain fibers placed into a Fabry–Perot cavity, in which one or two commercial high-power fiber Bragg gratings are used as in-fiber selective mirrors. The evolution of the lasers’ spectra with increasing laser power, including variations in the laser wavelength and spectrum width, is discussed.