Yellow to violet upconversion processes of Nd3+ in neat Cs2NaNdCl6 elpasolite

Yellow to violet upconversion of Nd3+ in neat Cs2NaNdCl6 elpasolite is demonstrated in this paper. Three intense bands have been observed at 367, 390 and 422 nm originating from 4D3/2 multiplet upon the excitation of 595.5 nm, which is in resonance with the energy of 4G5/2 level of Nd3+. The mechanism of the upconversion has been investigated through upconversion emission intensity dependence on the power of the pumping light and luminescence decay. It is found out that the upconversion is a two-photon process. The ground state absorption (GSA)/energy transfer upconversion (ETU) is responsible for the upconversion with comparison of the excitation spectrum and the one-photon absorption spectrum.