Optical investigation of Er³⁺ and Er³⁺/Yb³⁺ doped zinc-tellurite glass for solid-state lighting and optical thermometry

Er³⁺ and Er³⁺/Yb³⁺ doped zinc tellurite (ZnO/TeO₂) glasses were prepared using melt quenching technique. Spectroscopic properties of the glasses were studied by absorption spectroscopy, luminescence spectroscopy, and color chromaticity coordinates (CIE-1931) measurements. Upconverted-emission intensities and the CIE-1931 coordinates were strongly affected by the presence of Yb³⁺ ion, as well as the excitation power density of 975 nm laser light. Effect of temperature on green upconverted-emissions from two thermally coupled ²H_11/2 and ⁴S_3/2 levels of Er³⁺ ions were measured and fluorescence intensity ratio technique was applied to investigate the temperature sensing properties. High sensitivity and short response time properties make ZnO/TeO₂ glasses a very good candidate for non-contact optical temperature sensor applications. The maximum sensitivity of the glasses doped with Er³⁺ and Er³⁺/Yb³⁺ were found to be 72 × 10⁻⁴ K^-1 and 120 × 10⁻⁴ K⁻¹ at 429 K, respectively which are much higher than previously reported temperature sensors based on Er³⁺ ion doped materials. Hence, Er³⁺/Yb³⁺ doped zinc-tellurite glass can be more suitable than that of doped with Er³⁺ ions only for color tunable solid-state lighting and non-contact optical thermometry applications.