Low temperature time resolved photoluminescence of the 3.1 and 4.2 eV emission bands in Ge-doped silica

Time resolved photoluminescence (PL) has been performed on Ge-doped silica preform in the temperature range 10 to 295 K. Under pulsed KrF laser (5 eV) the well known alpha and beta emissions have been recorded at different delays from excitation. An accurate analysis of the time resolved spectra taken at different temperatures has shown the composite property of the two PL structures. At room temperature a components (alpha(1), alpha(2)) are peaked at 4.09 and 4.26 eV with a decay lime of about 10 ns. The peak energies of beta(1) and beta(2) components are calculated at 3.03 and 3.21 eV with lifetimes of 111 and 94 mu s, respectively. As temperature is decreased, alpha(1) and alpha(2) display the normal behaviour increasing in intensity down to 125 K; on the contrary, in the same temperature range, beta(1) and beta(2) undergo a quenching of their intensities. Taking into account their mutual spectral characteristics, alpha(1) has been correlated to beta(1) and alpha(2) to beta(2). The two sets of emission bands are tentatively attributed to a single center stabilized in different environments of the glassy matrix. (C) 1997 Elsevier Science B.V.