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

Abstract

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.