Changing the sample's temperature from 200 K to 535 K, we observed 670-fold enhancement of a phonon-assisted upconversion emission at ≈754 nm obtained from a Nd3+-doped tellurite glass excited by 5 ns laser pulses at 805 nm. A rate-equation model, including the relevant energy levels and temperature dependent transition rates, is proposed to describe the process. The results fit well with the data when one considers the nonradiative transitions contributing for the 754 nm luminescence are promoted by an effective phonon mode with energy of 700 cm-1.
Bibliographical noteFunding Information:
This work was supported by the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), through the INCT de Fotônica project and by a joint grant from CNPq and FACEPE (Fundação de Amparo à Ciência e Tecnologia do Estado de Pernambuco) through the PRONEX program. The authors are grateful to Dr. Kelly C. Jorge for helping with the Mathcad code. ®