Visible quantum cutting through downconversion in Eu~(3+)-doped KGd_(3)F_(10) and KGd_(2)F_(7) crystals

摘要

Visible quantum cutting (visible two-photon luminescence) through downconversion is observed for the Gd~(3+)-Eu~(3+) couple in Eu~(3+)-doped KGd_(3)F_(10) (KG3F) and KGd_(2)F_(7) (KG2F). The dependence of the efficiency of cross-relaxation required for visible quantum cutting on the Eu~(3+)-doping concentration and crystal structure is discussed in terms of the probability of energy transfer as a function of the rare-earth interatomic distance. Eu~(3+)-doped KG3F exhibits a higher efficiency in the cross-relaxation step than Eu~(3+)-doped KG2F. The highest efficiency of the cross-relaxation step, 0.65, is obtained for the KG3F crystal doped with 2 at. % Eu~(3+). It is also suggested from dependence of the lifetime of ~(5)D_(0) emission of Eu~(3+) in KG3F on Eu~(3+) concentration that interactions between rare-earth ions are strong at greater than 2 at. % Eu~(3+).