Emission spectroscopy and energy transfer in Tm3+, Tm3+-Ho3+, and Tm3+-Yb3+ doped tellurite fibers

This paper examines the steady state and time resolved emission spectroscopy of Tm3+ doped and Tm3+-Ho3+, Tm3+-Yb3+ co-doped tellurite fibers for mid-IR fiber laser design which find applications for lidar. These doped fibers show promising properties for compact and tunable laser sources in the visible and mid-IR when pumped at 800 nm, 980 nm and 1480 nm which can be used for remote chemical sensing and atmospheric monitoring. Tellurite glass has a lower cut-off phonon energy than silica glass and is more environmentally stable than fluoride glass, and coupling these properties with its high rare-earth ion solubility and high refractive index make this glass a very interesting material in which to study the fluorescence properties of these rare earth ions. We have measured the mid-IR fluorescence properties in varying lengths of multi-mode and single-mode fiber for the 3H4-3H6 (~1.85 μm), 3H4-3F4 (~1.46 μm) transitions in Tm3+ and the 5I7-5I8 (~2.05 μm) transition in Ho3+. We have also measured the visible emission from these fibers due to excited state absorption (ESA) as there is blue and green emission in Tm3+ and Tm3+-Ho3+ doped fibers respectively when pumped at 800 nm, and strong red and blue emission in the Tm3+-Yb3+ when pumped at 980 nm. These results in fiber are compared to bulk glass results and are used to describe the pumping schemes and energy transfer mechanisms of these rare earth ions in tellurite fiber.