LOW-TEMPERATURE TIME-RESOLVED PHOTOLUMINESCENCE OF THE 3.1 AND 4.2 EVEMISSION BANDS IN GE-DOPED SILICA

Time resolved photoluminescence (PL) has been performed on Ge-doped si lica preform in the temperature range 10 to 295 K. Under pulsed KrF la ser (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 composi te 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 a re calculated at 3.03 and 3.21 eV with lifetimes of 111 and 94 mu s, r espectively. As temperature is decreased, alpha(1) and alpha(2) displa y the normal behaviour increasing in intensity down to 125 K; on the c ontrary, in the same temperature range, beta(1) and beta(2) undergo a quenching of their intensities. Taking into account their mutual spect ral characteristics, alpha(1) has been correlated to beta(1) and alpha (2) to beta(2). The two sets of emission bands are tentatively attribu ted to a single center stabilized in different environments of the gla ssy matrix. (C) 1997 Elsevier Science B.V.