Infrared to visible up-conversion study for erbium-dopedzinc tellurite glasses

Abstract

Optical absorption and photoluminescence properties of Er3+-doped70TeO2-30ZnO glass are investigated. Judd-Ofelt intensityparameters of Er3+ have been determined to calculate the radiativetransition probabilities and the radiative lifetimes of excited states. Aninfrared to visible up-conversion was observed at room temperature in thistellurite glass system using a 797 nm excitation line. A study of the 4S3/2-4I15/2 transition (554 nm) versus power excitationprovided evidence for a two-step up-conversion process under this excitation.A red emission (663 nm) originating from the 4F9/2-4I15/2 transition has been observed as well. It was found that theefficiency of this up-conversion line is enhanced considerably with the Er3+ concentration relative to the green emission (554 nm). Thisbehaviour has been explained in terms of an energy transfer between excitedions. The temperature dependence of up-conversion intensity has been alsostudied in the range 40-310 K. It was found that the thermal quenching of thegreen emission (4S3/2-4I15/2) is large enoughcompared with those of the red transition (4F9/2-4I15/2 ). This thermal quenching has been discussed using the Riseberg andMoos model of multiphonon emission. It has been shown that the latter approachis not consistent with existing results. A complete analysis of thetemperature-dependent up-conversion has been made using an additional decayrate which may be attributed to a non-radiative energy transfer and/or acharge transfer through trapping impurities. A good agreement has beenachieved between measured and computed data.