Broadband near-infrared photoluminescence and energy transfer in Tm3+/Er3+-codoped low phonon energy gallate bismuth lead glasses

Tm3+/Er3+-codoped gallate bismuth lead (GBL) glasses are prepared and characterized optically. Broadband near-infrared fluorescence spectra composed of Er3+ 1.53 μm emission from the 4I13/2 → 4I15/2 transition and Tm3+ 1.47 μm emission from the 3H4 → 3F4 transition are recorded under 793 nm excitation wavelength. The full-width at half-maximum of the broad emission band depends on the Tm3+-Er3+ concentration ratio ([Tm]/[Er]), and a maximum bandwidth of 165 nm is achieved when the concentration ratio reaches 4, and the lineshape characteristic of the broadband emission remains the same for a fixed concentration ratio. The energy transfer processes involved are proposed and discussed, and the primary processes responsible for the flat broadband emission can be ascribed to the [Tm3+(3H4) + Tm3+(3H6)] → [Tm3+(3F4) + Tm3+(3F4)] and [Tm3+(3H4) + Er3+(4I15/2)] → [Tm3+(3F4) + Er3+(4I13/2)] processes. An investigation on energy transfer with assistance of matrix phonons shows that the matrix phonons play an important role in bridging the energy gap in the energy transfer processes.