Cr 3+–Tm 3+ energy transfer in alkali silicate glasses

Abstract

Optical absorption and emission spectra of alkaline silicate glasses doped with Cr 3+ and Tm 3+ ions show overlap of the Cr 3+ emission with the Tm 3+ absorption, indicating the possibility of energy transfer processes between these ions. Radiative and non-radiative energy transfer from optically excited Cr 3+ to Tm 3+ has been studied in three different alkaline disilicate glasses as a function of Tm 3+ concentration. The energy transfer parameter C DA and the transfer efficiency η t involved in the non-radiative energy transfer process have been obtained in the 13–300 K temperature range from the analysis of the Cr 3+ emission decay curves. The existence of a site distribution for Cr 3+ ions causes non-exponential decay curves even in glasses without Tm 3+ ions. These curves have been fitted to a modified Inokuti–Hirayama model considering a Gaussian distribution for the Cr 3+ ions. The results obtained are consistent with an electric dipole interaction mechanism. High transfer efficiencies, close to one, have been found in glasses codoped with 0.1 mol% Cr 3+ and 2 mol% Tm 3+.