Multiphonon energy gap law in rare-earth doped chalcogenide glass

The parameters for multiphonon relaxation of rare earth (RE) ions in the sulfide glass Ge25As8.33Ga1.67S65 have been re-evaluated using the temperature dependence of the fluorescence lifetime to separate out true multiphonon decay from other non-radiative processes, It is found that for energy gaps to the next lowest level greater than 2500 cm(-1), other non-radiative processes become dominant over multiphonon decal. The most likely process for this additional nonradiative decay is energy transfer to vibrational impurities such as OH and SH. The newly derived parameters lead to an electron- phonon coupling parameter epsilon = 0.058. which is more in line with other glass types than the previously accepted value of epsilon = 0.36. These new multiphonon relaxation parameters and the existence of additional non-radiative decay mechanisms has implications for the modeling of chalcogenide-based active devices. (C) 2003 Elsevier Science B.V. All rights reserved.