Enhancement of the Er3+ luminescence in Er-Ag co-doped Li2B4O7 glasses

Luminescence properties of the Er-doped and Er-Ag co-doped glasses with Li2B4O7 (Li2O-2B2O3) basic composition are investigated and analysed. The Li2B4O7 glasses of high chemical purity and optical quality, doped with Er and co-doped with Er and Ag were obtained in the air using standard glass technology. Spectroscopic properties of the Li2B4O7:Er and Li2B4O7:Er,Ag glasses were studied using optical absorption and photoluminescence (excitation, emission, decay kinetics) experimental techniques as well as Judd-Ofelt analysis. The theoretical and experimental oscillator strengths for observed absorption transitions as well as Judd-Ofelt intensity parameters (Ω2, Ω4, Ω6) have been calculated. Photoluminescence spectra of the Li2B4O7:Er and Li2B4O7:Er,Ag glasses reveal intense infrared (4I13/2 → 4I15/2 transition, λmax = 1530 nm) and green (4S3/2 → 4I15/2 transition, λmax = 546 nm) emission bands. Radiative properties such as transition probabilities (Arad), luminescence branching ratios (β), stimulated emission cross-sections (σem), and radiative lifetimes (τrad) are estimated. Experimental and radiative lifetimes were compared and quantum efficiency (η) has been evaluated. Considerable enhancement of the Er3+ green luminescence in the Li2B4O7:Er,Ag glasses has been observed. The observed enhancement is attributed to energy transfer from Ag+ to Er3+ ions as well as local field effects induced by surface plasmon resonance of the silver metallic nanoparticles.