Down- and up-conversion emissions in Er3+–Yb3+ codoped TeO2–ZnO–ZnF2 glasses

7 págs.; 10 figs.In this work, we report the near infrared and upconversion emissions of Er3+–Yb3+ codoped fluorotellurite TeO2–ZnO–ZnF2 glasses for different YbF3 concentrations ranging between 0.5 and 2 wt%. The study includes absorption and emission spectra and lifetime measurements for the infrared and visible fluorescence. The energy transfer between Yb3+ and Er3+ ions is confirmed by the temporal behavior of the near-infrared luminescence of Yb3+ ions as well as by the enhancement of the 1532 nm emission of Er3+ ions in the codoped samples. The Yb3+→Er3+ energy transfer efficiency is calculated from the Yb3+ lifetimes in single and codoped samples. Back transfer from Er3+ to Yb3+ ions is present under near infrared and visible excitation of Er3+ ions at 798 and 488 nm respectively. An enhancement of the visible upconversion fluorescence is also observed in the codoped samples due to energy transfer from Yb3+ to Er3+ ions. The standardized value for the efficiency of the green upconversion emission is 1.06×10−4 for the codoped sample with 2 wt% of YbF3 which is comparable to that reported in lead–zinc–tellurite glasses. The possible upconversion processes and mechanisms leading to the population of several excited levels are discussed.This work has been supported by the Spanish Government MINECO (Projects MAT2009-14282-C02-02, MAT2009-14282-C02-01, FIS2011-27968, and MAT2013-48246-C2-2-P) and the Basque Country Government (Project IT-659-13). A. Miguel and R. Morea acknowledge FPI grants from the Spanish Government.Peer Reviewe