Insight into neodymium clusters and spectroscopic properties in CaF2 single crystals

Abstract

In this work, the relationship between local structures and the photoluminescence parameters of neodymium activated fluorite crystals has been preliminary investigated in CaF2 crystals. The first principles calculation results reveal that as the size of codoped rare earth ions become smaller, the corresponding stable clusters twists progressively from cubic sublattice to square antiprism. The regulated spectral line properties and the concentration dependent photoluminescence parameters, including the absorption, emission and decays, agree well with the calculated results. In detail, the cubic stable clusters of Nd3+,La3+:CaF2 and Nd3+,Gd3+:CaF2 crystals possess similar spectral characteristics, while the other category of Nd3+,Y3+:CaF2 and Nd3+,Lu3+:CaF2 resembles both in the square antiprism cluster structures and spectra. Besides, a crystal with ultra long lifetime near 600 µs, wide emission bandwidth and high thermal conductivity has been obtained, which is promising for generation of the LD-pumped ultrafast lasers. By connecting the enriched spectral properties with local structures, it is highly expected to design new laser materials through regulating the local structures of active ions in rare earth doped fluorite crystals.