Energy transfer and 1.8 μm emission in Er3+/Tm3+ co-doped fluorogermanate glasses

Abstract

The 1.8μm down-conversion emission properties of Er3+/Tm3+ co-doped fluorogermanate glasses are investigated under 980nm laser diode (LD) excitation in this paper. The glass properties are systematically evaluated by DSC, XRD, Raman techniques. The spectroscopic properties of Er3+ and Tm3+ including infrared down-conversion (DC) and visible up-conversion (UC) emissions are studied in detail. Meanwhile, the up-conversion emissions at 542nm, 654nm of Er3+ are suppressed with a high amount of Tm2O3 added. The Judd-Ofelt parameters and spontaneous transition probability of Tm3+ are illustrated for radiative properties. Besides, the absorption and emission cross sections of Tm3+ in Er3+/Tm3+ co-doped fluorogermanate glasses are provided as potential candidates for mid-infrared applications. The possible energy transfer mechanism is investigated via simplified energy level diagram, and energy transfer efficiency from Er3+ to Tm3+ is as high as 85.9%. In addition, the energy transfer parameters between Er3+ and Tm3+ are analyzed by the phonon sideband theory. The results indicate that the Er3+/Tm3+ co-doped fluorogermanate glasses have potential applications in mid-infrared lasers.