Structural, luminescence and nonlinear optical properties of erbium doped barium tellurite glasses for photonic applications

Thermally stable erbium-doped barium tellurite [60TeO₂–20ZnO–4BaF₂–(16 − x)BaCO₃–xEr₂O₃, 0 ≥ x ≤ 2] glasses have been investigated for their linear and nonlinear optical properties. Significant concentration-dependent effects of erbium have been observed in most of the properties. Structural changes have been related to the formation of non-bridging oxygen atoms. Non-monotonic changes in physical and optical properties around 0.75 mol% doping indicated the network breaking and void filling ability of rare earth ions. Radiative lifetime of ⁴I_13/2 level increased with erbium concentration to 2.64 ms for x = 2, while the luminescence intensity for 1.5 μm emission corresponding to ⁴I_13/2 → ⁴I_15/2 transition decreased beyond 0.75 mol% indicating the concentration quenching effect in the sample. This indicates the need for suitable compositional tunability to achieve the maximum output at suitable doping levels of erbium. Samples showed reverse saturable absorption phenomena owing to two-photon absorption. Significant higher optical nonlinearity led to lower optical limiting thresholds with values between 2.749 and 3.930 × 10¹² W/m², indicating their effectiveness as good optical limiting materials along with their lasing ability.