Enhanced broadband 18 μm emission in Bi/Tm^3+ co-doped fluorogermanate glasses

Enhanced broadband 1.8 μm emission has been demonstrated in Bi/Tm3+ co-doped fluorogermanate glasses under a selectable pumping scheme. Detailed studies based on structure analysis, absorption spectra, excitation and emission spectra, and dynamic luminescence decay curves indicate that the enhanced broadband 1.8 μm luminescence originates from extremely efficient energy transfer process from Bi to Tm3+. Furthermore, the detailed energy transfer mechanism between Bi and Tm3+ is rationally analyzed. This novel pumping scheme and sensitizing mechanism of Bi/Tm3+ co-doping could provide the experimental basis for ~2.0 μm laser flexibly pumped by visible lasers, optical parametric oscillators, commercial 808 and 980 nm laser diodes.