Thermal effects on the optical spectra of Al2O3:Ti3+

Abstract

The results of an investigation of thermal effects on the fluorescence spectra of Ti³⁺ in sapphire are presented. As‐grown samples synthesized by the Czochralski method were found to exhibit a fluorescence band characteristic of Ti⁴⁺. After thermal annealing this band was greatly reduced and the Ti³⁺ fluorescence was seen. The fluorescence lifetime was found to be constant between 10 and 300 K and then to decrease significantly as temperature was raised to 500 K. This decrease is shown to be associated with thermal activation to the higher Jahn–Teller component of the excited state. The temperature dependences of the intensities, widths and lifetimes of the two zero‐phonon lines were monitored between 10 and 80 K. The lifetimes remained constant as the widths broadened and intensities decreased with temperature.The intensity change is associated with the increased rate of vibronic emission while the line broadening is attributed to the phonon processes coupling spin‐orbit components of the ground state and to Raman scattering of phonons.