Narrow linewidth and widely tunable operation of Tm-doped fiber laser with volume Bragg gratings

High power and widely tunable operation of Tm-doped silica fiber laser around 2 μm has been demonstrated using volume Bragg grating as the wavelength selection and spectrum narrowing element. The operating wavelength was continuously tunable from 1930 to 1821 nm, with > 52 W output power over a tuning range of 104 nm and a relatively narrow spectra width of < 15 pm. Over 60.8 W of diffraction limited (M2 ~ 1.5) CW output power was generated for 137 W of launched pump power, corresponding to a slope efficiency with respect to launched pump power of 46%. Output characteristics with a conventional replica diffraction grating for wavelength selection were also investigated as a comparison with that of using a volume Bragg grating. A maximum output power of 30.6 W at 1963 nm was generated for 79 W of launched pump power and the lasing wavelength could be tuned over 196 nm from 1859 to 2055 nm at output power levels in excess of 20 W. The bandwidth of the laser output was ~ 0.8 nm.