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.