Judd-Ofelt analysis of thulium-doped alumino-silicate optical glass prepared by MCVD combined with nanoparticle doping

Abstract

In this work, we present a comprehensive theoretical evaluation of Judd-Ofelt (JO) analysis for thulium-doped alumino-silicate glass in a wide range of compositions. The optical fiber preforms containing 5-10 mol. % Al(2)O(3) and 0.1-1.3 mol. % Tm(2)O(3) were prepared via the MCVD method combined with nanoparticle doping. The absorption spectra were measured, the absorption cross sections were evaluated and Judd-Ofelt (JO) analysis was carried out. The JO intensity parameters were found in the ranges Ω(2) = (6.1-6.6)center dot 10(-20) cm(-2), Ω(4) = (2.3-2.9)center dot 10(-20) cm(-2) and Ω(6)= (1.0-1.5)center dot 10(-20) cm(-2). These JO parameters, along with the calculated transition probabilities, branching ratios and radiative lifetimes showed relatively small variations across all measured samples. The calculated spectroscopic parameters may thus be used in theoretical calculations and simulations for materials in a wide range of compositions. Furthermore, the calculated radiative lifetime of the first excited level, (3)F(4), was around 4 ms for the nanoparticle-doped preforms. The fluorescence lifetime was then measured and found to decrease from 0.9 ms to 0.7 ms with increasing concentration, providing values of quantum efficiency in the 17-22 % range. These values are significantly higher than 10 % determined for a reference solution-doped optical fiber preform and from literature, demonstrating the beneficial contribution of the nanoparticle doping method on the resulting quantum efficiency.