Cr3+-Tm3+ energy transfer in alkali silicate glasses

Optical absorption and emission spectra of alkaline silicate glasses doped with Cr3+ and Tm3+ ions show overlap of the Cr3+ emission with the Tm3+ abs orption, indicating the possibility of energy transfer processes between th ese ions. Radiative and non-radiative energy transfer from optically excite d Cr3+ to Tm3+ has been studied in three different alkaline disilicate glas ses as a function of Tm3+ concentration. The energy transfer parameter C-DA and the transfer efficiency eta (t) involved in the non-radiative energy t ransfer process have been obtained in the 13-300 K temperature range from t he analysis of the Cr3+ emission decay curves. The existence of a site dist ribution for Cr3+ ions causes non-exponential decay curves even in glasses without Tm3+ ions. These curves have been fitted to a modified Inokuti-Hira yama model considering a Gaussian distribution for the Cr3+ ions. The resul ts obtained are consistent with an electric dipole interaction mechanism. H igh transfer efficiencies, close to one, have been found in glasses codoped with 0.1 mol% Cr3+ and 2 mol% Tm3+. (C) 2001 Elsevier Science B.V. All rig hts reserved.