Heavily erbium-doped low-hydroxyl fluorotellurite glasses for 27 μm laser applications

Abstract

Heavily erbium-doped low-hydroxyl fluorotellurite glasses with molar compositions of (85.7−x)TeO2 + xBaF2 + 4.8Na2CO3 + 9.5Er2O3 (x = 38.1, 28.6, 19) were fabricated. The maximum doping concentration of erbium ions was up to 19 mol % by introducing BaF2 into the tellurite glass system. Under 980 nm excitation, intense emissions around 2.7 μm from the 4I11/2 → 4I13/2 transition of Er3+ ions were observed in these glasses. The efficient mid-infrared emission can be attributed to the existence of cross relaxation (CR) 4I13/2 → 4I15/2 (Er3+): 4I13/2 → 4I9/2 (Er3+) caused by high erbium concentration, low hydroxyl content, and low phonon energy. The stimulated emission cross section at 2.7 μm of 47.6TeO2 + 38.1BaF2 + 4.8Na2CO3 + 9.5Er2O3 glass was calculated as 1.94 × 10−20 cm2. Our results indicate that it is a promising gain medium for 2.7 μm lasers.