2.85 µm fluorescence of Ho-doped water-free fluorotellurite glasses

Holmium doped fluorotellurite glasses with composition of xHo2O3 (wt%)+60TeO2–30ZnF2–10NaF (mol%) (xHo-TZNF60, x=0.50–1.50) were synthesized by physical and chemical dehydration technique (PCDH) and characterized as candidates of fiber laser glasses. Intense 2.85 µm fluorescence (Ho3+: 5I6→5I7) was observed experimentally when excited at 1163 nm. It is attributed to low phonon energy of fluoride component and water-free characteristic (αOH=0.027 cm−1). Ho-TZNF glass possess a large simulated emission cross-section of 1.51×10−20 cm2, a long fluorescence lifetime of ~0.81 ms (1/e time of the initial part of non-exponential decay curve) and a broad transparent window of 2.1–4.2 µm. Among all the compositions of glass samples, 1.00Ho-TZNF60 is the optimized one, and thus is proposed to be the most potential material for 3.0 µm fiber laser.