Investigation of the mechanism of nonradiative relaxation of the 4F3/2 metastable state of Nd3+ in silicate glass

An investigation was made of the kinetics of the decay of the ⁴F_3/2 metastable state of Nd³⁺ in silicate glass. The investigation was carried out in a wide range of neodymium activator concentrations and the dynamic range of the luminescence intensity was 10³. The kinetics was practically constant throughout the luminescence line profile and it was not greatly affected by variation of the wavelength of the exciting radiation provided by several lasers (including a laser with a continuously tunable emission frequency). The relationship of the parameters of the multipole interactions, causing migration of energy and destruction of electronic excitation, to the decay kinetics was studied. The time dependence of the rate of nonradiative relaxation of the metastable state was determined experimentally. It was found that this relaxation was due to the dipole-dipole interaction between the particles. It was concluded that the activator ions were distributed inhomogeneously in the silicate matrix and that there were regions with higher local activator concentrations even when the overall Nd³⁺ concentration was very low.