Effects of Activator Ion Concentration on the Upconversion Processes in Er3+-Doped TeO2-ZnO Glass

Abstract

Photoluminescence properties of Er3+-doped 70TeO2–30ZnO glasses are investigated. Infrared to visible upconversion has been observed at room temperature in this tellurite glass using a 797 nm excitation laser. A study of the 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions versus excitation laser power shows evidence for a two-step upconversion process under this excitation. The red emission originating from the 4F9/2 → 4I15/2 transition is enhanced relative to the green emission with increasing Er3+ ion concentration. This behaviour has been explained as being due to an energy transfer between activator ions. The temperature dependence of the upconversion intensity has also been studied in the range 60–310 K. It was found that the red emission of 4F9/2 → 4I15/2 grows considerably relative to the green transition with increasing temperature in heavily doped samples. This indicates that energy transfer mechanisms, responsible for the red emission enhancement, are temperature dependent.