Radiative and non-radiative relaxation of rare-earth ions in Ga_2S_3-GeS_2-La_2S_3 glasses

摘要

Spectroscopic properties of Nd~(93+) and Ho~(3+) in a Ga_2S_3-GeS_2-La_2S_3 glass system were investigated on the basis of the Judd-Ofelt analyses for 60GaS_(3/2) centre dot 10GeS_2 centre dot 27LaS_(3/2) centre dot 3LnS_(3/2) glasses (Ln = Nd or Ho) and emission lifetime measurements for 60GaS_(3/2) centre dot 10GeS_2 centre dot 29.7LaS_(3/2) centre dot 0.3LnS_(3/2) glasses (Ln = Nd or Ho). The obtained Judd-Ofelt #OMEGA#_2 parameter for Nd~(3+) was larger than those of other glass systems such as oxides and fluorides. For Ho~(3+), 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 ~4G_(5/2) and ~2K_(13/2) levels of Nd~(3+) and ~5F_5 and ~5S_2 levels of Ho~(3+) 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 ~5S_2 of Ho~(3+) was about one order larger than predicted from the so called 'energy-gap law'. We assumed that the energy transfer from the ~5S_2 of Ho~(3+) to an electronic state of the host glass occurs. Multiphonon relaxation rates were comparable with those of a ZnCl_2-based glass.