Publication

Abstract : Optimizing Er3 + concentration is vital for efficient near-infrared (NIR) and up-conversion (UC) luminescence concurrently in photonic glass hosts. In this work, it is hypothesized that controlled incorporation of Er2O3 into lithium-calcium-bismuth-borate (LCBB) glasses can modify the local glass structure and regulate radiative and non-radiative (NR) processes, thereby enhancing both NIR and UC emission characteristics. To verify this hypothesis, a series of Er2O3-doped LCBB glasses containing 0.25–1.0 mol% Er2O3 were synthesized using the conventional melt-quenching method and systematically characterized through physical, structural, optical absorption, photoluminescence, up-conversion, lifetime, and McCumber analyses. The results reveal progressive structural depolymerization and the formation of non-bridging oxygens with increasing Er2O3 content, accompanied by an increase in the indirect optical band gap from 2.86 to 3.08 eV. Under 980 nm excitation, all glasses exhibit a broad NIR emission centered at 1532 nm, with the highest intensity observed for LCBBEr0.75, whereas the strongest green UC emission at 543 nm is obtained for LCBBEr0.25. Power-dependent studies confirm that the green UC emission is governed by a three-photon absorption process and exhibits excellent color purity (∼98%). At higher Er2O3 concentrations, concentration quenching and non-radiative energy transfer become prominent, leading to reduced UC intensity and shorter lifetimes. Furthermore, LCBBEr0.75 exhibits a higher emission cross-section (12.55 × 10−21 cm2) than absorption cross-section (10.46 × 10−21 cm2) at 1532 nm, along with a broad gain profile spanning the S-, C-, and L-bands, highlighting its potential for broadband optical amplification. These results indicate that Er2O3 concentration plays a crucial role in governing the luminescence behavior of LCBB glasses, with LCBBEr0.75 and LCBBEr0.25 emerging as the optimal compositions for NIR amplification and green UC emission, respectively.