First-Principle Study of Optical Properties in Erbium-Doped Fibres for Enhanced Optical Signal Amplification

The optical properties of silica, essential for applications ranging from fibre optics to UV transmission windows, are closely linked to atomic-scale defects, even though they are challenging to identify. Although electron paramagnetic resonance (EPR) has long been the predominant technique for defect analysis, this study employs time-dependent density functional perturbation theory (TDDFPT) to systematically examine the understudied optical signatures of erbium (Er)-doped silica (SiO2) and native defects (oxygen/silicon vacancies). The Er-doped systems (2.08–6.25% concentrations) and pure SiO2 along vacancy defects were simulated to compute transmittance, reflectivity, dielectric characteristics, and absorption. The results showed that the absorption peaks and imaginary dielectric function (ɛ2) are redshifted by Er inclusion, with doping at 4.17% yielding the best improvement. Conversely, vacancy defects decrease otherwise because of increased absorption and reflection of the visible spectrum. These findings demonstrate how Er-doping can alter SiO2's optical response and emphasize the value of TDDFPT in connecting optical behaviour to defect patterns. This study advances the logical design of silica-based optoelectronic devices and offers a theoretical foundation for enhancing defect engineering in wide-gap semiconductors.