Enhanced 1.8 µm emission in Cr3+/Tm3+ co-doped fluorogermanate glasses for a multi-wavelength pumped near-infrared lasers

Cr3+/Tm3+ co-doped fluorogermanate glasses were prepared by melt-quenching technique, and their luminescent properties were investigated under excitation of Xenon lamp and 808 nm laser diode, respectively. Through strong sensitization of Cr3+, an enhanced 1.8 µm emission band of Tm3+: 3F4→3H6 can be achieved in an extremely extended excitation band of 380-900 nm. The possible energy transfer mechanism between Cr3+ and Tm3+ is rationally discussed. On the basis of experimental data, the highest energy transfer efficiency is up to 91.70%. Our results suggest this efficient Cr3+/Tm3+ co-doping system provides a selective pump mechanism for obtaining 1.8 µm laser and thus shows attractive applications in near-infrared fiber lasers and amplifiers.