Publication

Abstract : Achieving glasses with high gain, a large emission cross-section, and improved optical properties is a key requirement for optical amplifiers and optical fibers to meet current technological demand. Motivated by this, in the present study, Er2O3-doped lithium bismuth calcium borate glasses with compositions 10Li2O-20Bi2O3-xCaO-(70-x-y)B2O3-yEr2O3 (x = 10, 15 mol% and y = 0, 5 mol%) were synthesized via the melt-quenching technique to investigate their structural, optical, and spectroscopic properties for NIR photonic applications. XRD analysis shows the amorphous nature of the prepared samples. Raman analysis revealed that lower CaO and higher B2O3 contents favored a more polymerized borate network, with BO3 and BO4 structural units. Correspondingly, the optical band gap values estimated using Tauc's relation showed that the optimized B4 glass exhibited the highest indirect optical band gap of ∼2.67 eV. Furthermore, UV–Vis–NIR absorption spectra exhibited characteristic Er3+ transitions, and the experimental oscillator strengths showed good agreement with Judd–Ofelt (JO) calculations. The optimized B4 glass exhibited a significant increase in the JO intensity parameter Ω2 from 7.39 × 10−20 cm2 to 14.51 × 10−20 cm2, indicating enhanced asymmetry and covalency around Er3+ ions. Under 980 nm excitation, a strong NIR emission centered at ∼1530 nm corresponding to the 4I13/2 ➔ 4I15/2 transition was observed, with B4 glass showing higher emission intensity and broader bandwidth (∼41 nm) compared to B2 glass (∼37 nm), supported by the higher stimulated emission cross-section (σem = 2.3 × 10−20 cm2) and gain bandwidth (σem = 9.43 × 10−26 cm3) for B4 glass than B2 glass (2.1 × 10−20 cm2 and 7.77 × 10−26 cm3). The gain spectra showed a broad amplification bandwidth spanning 1450–1650 nm, with relatively flat gain across the C-band. The optimized B4 glass exhibited ∼96% higher Ω2, broader emission bandwidth (∼41 nm), and a wider amplification window spanning ∼1450–1650 nm, demonstrating its suitability for broadband optical amplifiers and WDM applications.