EFFECTS OF CHLORIDE INTRODUCTION ON THE OPTICAL-PROPERTIES AND THE UP-CONVERSION EMISSION WITH 980-NM EXCITATION OF ER3+ IN ZBLAN FLUORIDE GLASSES

Er-doped ZBLAN fluoride glasses and those containing chloride were pre pared. The parameters of optical transitions were determined experimen tally. By the introduction of chlorine as replacing NaF with NaCl up t o 20 mol% NaCl, the Judd-Ofelt parameters, Ohm(2), and Ohm(4), were in creased and the multiphonon-relaxation rate decreased. With these para meters inserted into the rate equations, they were numerically solved. The upconversion mechanisms of Er3+ With 980-nm excitation and the ef fects of chlorine in the samples on the upconversion processes were ob served. The upconversion processes for both 550-nm and 660-nm emission s were found to be dominated by the resonant and the phonon-assisted e nergy transfers. The intensity ratio of the 660-nm emission to the 550 -nm emission decreased with increasing NaCl content. This change of in tensity ratio was due to the suppression of the phonon-assisted energy transfer by chlorine. (C) 1997 Elsevier Science B.V.