Single-frequency thulium-doped distributed-feedback fiber-laser

We have successfully demonstrated a single-frequency distributed-feedback (DFB) thulium-doped silica fiber laser emitting at a wavelength of 1735 nm. The laser cavity is less than 5 cm long and is formed by intracore UV-written Bragg gratings with a phase shift. The laser is pumped at M nm from a Ti:sapphire laser and has,a threshold pump power of 59 mW. The laser has a, maximum output power of 1 mW in a single-frequency, single-polarization radiation mode and is tunable cover a few nanometers. To the best of the authors' knowledge, this is the first report of a single-frequency DFB fiber laser that uses thulium. as. the amplifying medium. The lasing wavelength is the longest demonstrated with DFB fiber lasers and yet is among the shortest obtained for thulium-doped silica fiber lasers. (C) 2004 Optical, Society of America.