Quantum cutting through downconversion in rare-earth compounds

A new concept for the conversion of vacuum ultraviolet radiation to visible light is described which makes it posible to obtain two visible photons for each vacuum ultraviolet photon absorbed (quantum cutting). The feasibilty of this concept, called downconversion, is demonstrated by two examples: LiGdF4 : EU3+ and LiGdF4 :Er3+, Tb3+. The highest efficiencies are achieved for LiGdF4 :Eu3+. Upon excitation of Gd3+ with a high-energy photon, two visible photons can be emitted through an efficient two-step energy transfer process, with a quantum efficiency that approaches 200%. (C) 2000 Elsevier Science B.V. All rights reserved.