Broadly tunable laser operation near 2 μm in a locally disordered crystal of Tm3+-doped NaGd(WO4)2

Output powers as high as 300 mW were obtained at 1925 nm in the cw regime with a Tm. laser operating at room temperature, either with Ti-sapphire or diode laser pumping, using a new single crystal of NaGd(WO4)(2) grown by the Czochralski method and doped with 5 mol. % of Tm3+ in the melt. This crystal belongs to the R tetragonal space group and exhibits a locally disordered structure due to the random occupancy of the same lattice sites by Na and Gd (or Tm) ions. The local disorder results in large bandwidths of the Tm3+ optical transitions (e.g., FWHM 60 cm(-1) at 5 K for the H-3(6)-> F-3(4) transition involved in the laser emission), which allows one to obtain one of the broadest laser tunability ranges, from 1813 to 2025 run (approximate to 17 THz), achieved with a Tm3+-doped crystalline material. A detailed characterization of the Tm3+ optical spectroscopy in this novel host was performed at 5 and 300 K. (c) 2006 Optical Society of America.