Mechanical strength is one of the biggest limitations of practical application for tellurite fiber. In this study, we design and fabricate a single mode tellurite composite fiber to overcome the flaw. The fiber has a double cladding structure with tellurite core and inner cladding, the outer cladding, which is made of non-tellurite glass, possesses of appropriate softening temperature and coefficient of thermal expansion, well matched the novelty tellurite glass. The propagation loss of the fiber is less than 0.02 dB/cm @1310 nm. We also investigate the laser property of the fiber by using a homemade watt-class 1590 nm fiber laser. 2 micron fiber laser is demonstrated with a 2 cm length of the fiber.
We investigate the spectroscopic and lasing performance of Tm3+-Ho3+ co-doped tungsten tellurite single mode fiber
operating around 2.1 μm with a commercial 800 nm diode laser pump source. The optimum doping concentration of
Tm2O3 and Ho2O3 in Tm3+-Ho3+ co-doped TeO2-WO3-La2O3 (TWL) glass is 1 mol% and 0.5 mol%, respectively. The lifetime of Ho3+:5I7 level is 3.3 ms in the bulk glass. The maximum stimulated emission cross-section of Ho3+ in TWL
is 10.0×10-21cm2. The tungsten tellurite single mode fibers are prepared by using rod-in-tube method. The infrared emission spectra are compared with varying fiber lengths. Tm3+-Ho3+ co-doped fiber shows weak emission at ~1.9 μm very strong emission at ~2.1 μm, which indicates efficient energy transfer from Tm3+ to Ho3+ in the fiber. The 1.47 μm emission increases with the increment of the fiber length, which means a back energy transfer from Ho3+ to Tm3+. A 106 mW continuous wave laser emission at ~2.1 μm is demonstrated from a 16 cm length of this fiber, the slope efficiency is 23%, corresponding to a 17% optical to optical efficiency. Lasing has also been achieved in <5 cm length of this fiber,
making this material a promising candidate for single frequency ~2.1 μm laser sources.