Optical and spectral characterization of Er³⁺/Yb³⁺-codoped NAT ceramics

Er³⁺/Yb³⁺-codoped aluminum oxide (Al₂O₃) modified tellurite ceramics have been prepared by high-temperature melting. Judd-Ofelt parameters of Eu³⁺, which was introduced in 15%Na₂O-15%Al₂O₃-70%TeO₂ (NAT) ceramic system as a probe, present a medium asymmetry and covalence environment around rare-earth ions. Efficient 551 nm green and 668 nm red two-photon pumped upconversion fluorescence and strong 1.533 μm infrared radiation were observed and recorded in the Er³⁺/Yb³⁺-codoped NAT ceramics under the excitation of ∼980 nm diode lasers. For 1.533 μm near-infrared emission, the maximum stimulated emission cross-section was calculated to be 6.61×10^-21 cm², and the ordinary exhibition referring to tellurite glass system is due to the lowering of refractive index, which is caused by the abundance of Al₂O₃ composition. Efficient visible upconversion and infrared emissions indicate that Er³⁺/Yb³⁺-codoped NAT ceramics are promising substrates in developing color light sources, upconversion display devices, infrared sensors and infrared radiation sources.