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Proceedings Paper

Photorefractive Measurement Of Anisotropy Of The Mobility Of Photo-Excited Holes In BaTiO[sub]3[/sub]
Author(s): Chyr-Pwu Tzou; Tallis Y. Chang; R. W. Hellwarth
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Paper Abstract

We have measured the anisotropy of the mobility of photo-excited holes in nominally undoped single-crystal, poled, ferroelectric BaTiO3 (p-BaTiO3) at room temperature. In this crystal, a photorefractive grating results from the spatial rearrangement of trapped holes which have been excited by light-intensity beats and then drift and diffuse before recombining at similar empty traps. The resulting Coulomb field grating gives rise to a refractive index grating (the "photorefractive grating") via the electro-optic effect. In this uniaxial crystal the mobility of the holes is different parallel (μ) or perpendicular (μ) to the crystal axis (c-axis). As is well known, a uniform light beam causes an established photorefractive grating to decay exponentially in time. We have measured this decay rate with the grating wavevector oriented at various angles to the c-axis and compared these rates with the prediction of the standard model which assumes simple drift and diffusion with direct recombination time T,1 as extended by us to allow different drift and diffusion rates parallel and perpendicular to the c-axis. The data is satisfactorily fit by this model if we use μ/μ = 18 ± 7 and = 5 x 10-1 cm2/Volt. We also require a ratio of dielectric constants el/e11 = 25 ± 15, which is consistent with the ratio measure-ments by other methods in other samples. To fit the data, we also needed values for the density of excitable traps (= 2 x 1016 cm-3) and photoconductivity parallel to the c-axis, which we took from previously published measurements on the same crystal. 2 Our measurements were made with 8 nsec pulses at A = 532 nm. We could see no effects of finite hole recombination time, which suggests that the recombination time must be less than 1 nsec. If this is true,and recombination is a direct process, then the mobility must be larger than 0.5 cm2/sec/Volt parallel to the c-axis.

Paper Details

Date Published: 16 June 1986
PDF: 1 pages
Proc. SPIE 0613, Nonlinear Optics and Applications, (16 June 1986); doi: 10.1117/12.960385
Show Author Affiliations
Chyr-Pwu Tzou, University of Southern California (United States)
Tallis Y. Chang, University of Southern California (United States)
R. W. Hellwarth, University of Southern California (United States)

Published in SPIE Proceedings Vol. 0613:
Nonlinear Optics and Applications
Pochi Yeh, Editor(s)

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