Radiative and non-radiative relaxation of rare-earth ions in Ga2S3-GeS2-La2S3 glasses

Spectroscopic properties of Nd3+ and Ho3+ in a Ga2S3-GeS2-La2S3 glass system were investigated on the basis of the Judd-Ofelt analyses for 60GaS(3/2) . 10GeS(2) . 27LaS(3/2) . 3LnS(3/2) glasses (Ln= Nd or Ho) and emission lifetime measurements for 60GaS(3/2) . 10GeS2 . 29.7LaS(3/2) . 0.3LnS(3/2) glasses (Ln = Nd or Ho). The obtained Judd-Ofelt Omega(2) parameter for Nd3+ was larger than those of other glass systems such as oxides and fluorides. For Ho3+, On the other hand, the Omega(2) parameter was so small that it could not be determined with enough accuracy. Non-radiative transition rates for (4)G(5/2) and K-2(13/2) levels of Nd3+ and F-5(5) and S-5(2) levels of' Ho3+ were obtained by the difference between the inverse of the measured emission lifetimes and the calculated radiative transition rates of these levels. The non-radiative transition rate of the S-5(2) of Ho3+ was about one order larger than predicted from the so called 'energy-gap law'. We assumed that the energy transfer from the S-5(2) of Ho3+ to an electronic state of the host glass occurs. Multiphonon relaxation rates were comparable with those of a ZnCl2-based glass. (C) 1999 Elsevier Science B.V. All rights reserved.