Studies of two-photon excitation and vacuum ultraviolet fluorescence in Nd: YLF

Two-photon ultraviolet laser excitation of Nd:YLiF4 was studied via the obs ervation of the vacuum ultraviolet fluorescence from localized states of th e 4F(2)5d configuration of the Nd3+ ion. Details of the laser excitation sc hemes, the fluorescence spectra, and the excitation laser intensity depende nce of the fluorescence signals an discussed. A series of experiments demon strated that the vacuum ultraviolet 4f(2)5d --> 4f(3) fluorescence spectrum following two-photon excitation is independent of the excitation laser wav elength. Our studies also revealed significant fluorescence reabsorption ef fects. Comparisons are made with earlier single-photon excitation studies i n this system. (C) 2000 Elsevier Science B.V. All rights reserved.