Concentration-dependent and enhanced luminescence in Ge_23.5Ga_11.5Se₆₅ glasses and glass-ceramics doped with Er³⁺

We have reported the fabrication and characterization of Ge_23.5Ga_11.5Se₆₅ glasses and glass-ceramics with different Er³⁺ concentrations. It was found that, the emission properties of the bulk glasses showed the fluorescence intensity and lifetime increased until they reached a maximum, and then decreased with increasing Er³⁺ concentration. This is due to concentration quenching effect although the maximum dissolving concentration of Er³⁺ can be up to ∼1 wt% of Er. A careful thermal process has led to the formation of ∼80 nm β-Ga₂Se₃ crystalline particles in Ge_23.5Ga_11.5Se₆₅ glasses doped with 0.8 wt% of Er³⁺. By monitoring ⁴I_13/2 → ⁴I_15/2 Er³⁺ transition, almost fourfold enhancement in the intensity and ∼0.57 ms prolongation in the lifetime of near-infrared fluorescence at 1.54 μm have been observed after crystallization. It was assigned to the decreasing phonon energy of the local environment of Er³⁺ ions during the crystallization.