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

Tm 3+ /Er 3+ -codoped gallate bismuth lead (GBL) glasses are prepared and characterized optically. Broadband near-infrared fluorescence spectra composed of Er 3+ 1.53 µm emission from the 4 I 13/2 → 4 I 15/2 transition and Tm 3+ 1.47 µm emission from the 3 H 4 → 3 F 4 transition are recorded under 793 nm excitation wavelength. The full-width at half-maximum of the broad emission band depends on the Tm 3+ –Er 3+ 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 [Tm 3+ ( 3 H 4 ) + Tm 3+ ( 3 H 6 )] → [Tm 3+ ( 3 F 4 ) + Tm 3+ ( 3 F 4 )] and [Tm 3+ ( 3 H 4 ) + Er 3+ ( 4 I 15/2 )] → [Tm 3+ ( 3 F 4 ) + Er 3+ ( 4 I 13/2 )] 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.