title: Hologram recording via spatial density modulation of Nb(Li)(4+/5+) antisites in lithium niobate.
abstract: Hologram recording is studied in thermally reduced, nominally undoped lithium niobate in the time domain from 10 ns to 100 s by means of intense ns pump laser pulses (λ = 532 nm) and continuous-wave probe light (λ = 785 nm). It is shown that mixed absorption and phase gratings can be recorded within 8 ns that feature diffraction efficiencies up to 23 % with non-exponential relaxation and lifetimes in the ms-regime. The results are explained comprehensively in the frame of the optical generation of a spatial density modulation of Nb(Li)(4+/5+) antisites and the related optical features, i.e. absorption as well as index changes mutually related via the Kramers-Kronig-relation. Implications of our findings, such as the electrooptical properties of small bound Nb(Li)(4+) polarons, the optical features of Nb(Li)(4+):Nb(Nb)(4+) bipolarons, Nb(Nb)(4+) free polarons and O-hole-polarons, the impact of light polarization of pump and probe beams as well as of the polaron density are discussed.
authors.affiliation: Department of Physics, University of Osnabrück, Barbarastr 7, 49069 Osnabrück, Germany. mimlau@uos.de
authors.forename: M
authors.initials: M
authors.lastname: Imlau
authors.forename: H
authors.initials: H
authors.lastname: Brüning
authors.forename: B
authors.initials: B
authors.lastname: Schoke
authors.forename: R-S
authors.initials: RS
authors.lastname: Hardt
authors.forename: D
authors.initials: D
authors.lastname: Conradi
authors.forename: C
authors.initials: C
authors.lastname: Merschjann