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 fo r each vacuum ultraviolet photon absorbed (quantum cutting). The feasibilty of this concept, called downconversion, is demonstrated by two examples: L iGdF4 : EU3+ and LiGdF4 :Er3+, Tb3+. The highest efficiencies are achieved for LiGdF4 :Eu3+. Upon excitation of Gd3+ with a high-energy photon, two vi sible 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.