Energy transfer and 1.8 μm emission in Yb3+/Tm3+ co-doped bismuth germanate glass

This study presents the luminescent properties of Yb3+/Tm3+ co-dopant ions inside a new host glass based on bismuth germanates. Judd–Ofelt intense parameters, radiative transition rate, radiative lifetime, and branching ratios of Tm3+ in the present glass are calculated based on the absorption spectrum. A strong 1.8 μm emission was observed in the Yb3+/Tm3+ co-doped bismuth germanate glass upon the excitation of a conventional 980 nm laser diode. Using a spectral overlap model, the micro parameter for direct energy transfer from Yb3+ ions to Tm3+ ions (CDA) was found to be almost 30 times larger than the back energy transfer from Tm3+ ions to Yb3+ ions (CAD). The linear dependence of energy transfer probability on the co-dopant concentration exhibits that the energy transfer is assisted by energy migration among donor ions. The large energy transfer efficiency (89%) indicates that the Yb3+/Tm3+ co-doped bismuth germanate glass is a good candidate for the 1.8 μm laser.