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

We present a detailed Judd-Ofelt (JO) analysis of Ho3+-doped alumino-silicate optical fiber preforms in a wide range of compositions and prepared by both standard solution doping method as well as the more advanced nanoparticle doping. The absorption spectra were measured, the absorption cross sections were calculated for each observed transition and the Judd-Ofelt analysis was conducted. The preforms exhibited the values of JO parameters of Ω2 = (7.2 – 10.6) 10-20 cm2, depending on the Al2O3 content, and Ω4 and Ω6 around 2.5 and 1.2 10-20 cm2, respectively. The radiative transition parameters, such as transition probabilities, branching ratios and radiative lifetimes, were calculated. The radiative lifetime of the 5I7→5I8 transition, in the 16.1 – 17.2 ms range, combined with a measured value in the 0.9 – 1.9 ms range, was used to calculate the quantum efficiency, which was in the 5 – 11 % range. The preforms prepared by the nanoparticle doping containing high Al2O3 contents above 8 mol. % exhibited superior values of measured lifetime (above 1.5 ms) and quantum efficiency (above 8 %) compared to the standard solution-doped samples. To the best of our knowledge, this work is the first comprehensive report on the JO analysis of Ho3+-doped alumino-silicate glass, the calculated parameters may be used in the various calculations, simulations and modelling of holmium-doped fiber lasers and other devices.