Development of Nanoengineered Thulium-Doped Fiber Laser With Low Threshold Pump Power and Tunable Operating Wavelength

A tunable and low-threshold thulium (Tm)-doped fiber (TDF) laser is demonstrated using a new silica-based nanoengineered TDF in a linear configuration, in conjunction with 1552-nm pumping. The TDF used in these experiments had a Tm-doped nanoengineering yttrium-alumina-silica glass core with a diameter of 13.43 μm and 0.21 NA, which is surrounded by a pure silica inner cladding with normal acrylate polymer resin coating. The nanoengineered TDF was fabricated using a modified chemical vapor deposition (MCVD) process, in conjunction with a solution-doping technique. The fabricated fiber shows an absorption loss of 165 dB/m at 793 nm. A maximum lasing slope efficiency of 26.2% was obtained at a 1910-nm wavelength using the fabricated fiber with an optimum length of 5 m. The maximum output power of 138 mW was achieved at the maximum pump power of 1100 mW. The lowest pump power threshold of 693 mW for a 1552-nm wavelength was obtained at a TDF length of 7 m. The operating wavelength of the laser could be continuously tuned from 1890 to 1910 nm with an optical signal-to-noise ratio better than 43 dB, whereas the slope efficiency of the laser varies from 16.4% to 19.7%.