Ultraviolet photorefraction at 325 nm in doped lithium niobate crystals

The MOE Key Laboratory of Weak Light Nonlinear Photonics, Nankai University, Tianjin 300457, China and Photonics Center, School of Physics, Nankai University, Tianjin 300071, China
Journal of Applied Physics (Impact Factor: 2.18). 03/2010; 107(3):033113 - 033113-7. DOI: 10.1063/1.3305339
Source: IEEE Xplore


We studied the photorefractive effect of lithium niobate ( LiNbO 3) doped with Mg, Zn, In, Hf, or codoped with Mg and Fe at an ultraviolet (UV) wavelength down to 325 nm. It is found that the UV photorefraction of LiNbO 3 doped with Mg, Zn, In, or Hf was enhanced significantly as compared to that of the nominally pure LiNbO 3 . Our results show that the property of resistance against photorefraction in highly Mg, Zn, In, or Hf doped LiNbO 3 is true only in the visible and near-infrared wavelength range. By contrast, these crystals exhibit excellent photorefractive characteristics at UV wavelength of 325 nm, even better than those at 351 nm. For example, the photorefractive two-wave coupling gain coefficient Γ and the photorefractive recording sensitivity at 325 nm were measured to be ∼38 cm -1 and 37.7 cm/J, respectively, in a LiNbO 3 crystal doped with 9 mol   % Zn. The photorefractive response time of a Mg : LiNbO 3 with a 9 mol   % Mg was measured to be 73 ms with a total recording intensity of 614 mW / cm 2 at 325 nm. In highly Mg, Zn, In, or Hf doped LiNbO 3 crystals, diffusion dominates over photovoltaic effect and electrons are the dominant charge carriers in UV photorefraction at 325 nm. The results are also of interest to the study on the defect structure of LiNbO 3 near to the absorption edge.

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Available from: Jingjun Xu, Feb 20, 2015
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    • "Mg 2+ , Zn 2+ , In 3+ and Hf 4+ [6] "
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    ABSTRACT: The infrared spectra of stoichiometric LiNbO3 crystals containing photorefractive damage resistant ions (e.g. M = Mg, Zn, Sc, In, Hf, Zr or Sn) above their threshold concentration reveal OH- absorption bands absent in undoped crystals. The bands are attributed to stretching vibrations of hydroxyl ions in M-Nb(n+) OH- (n = 2, 3 or 4) type defect complexes. The higher the valency of the dopant ion the lower the observed frequency of the hydroxyl vibration in the complex, and the closer the O-H bond direction to the oxygen plane perpendicular to the crystallographic c axis of the crystal.
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    ABSTRACT: Near-stoichiometric LiNbO3 single crystal tri-doped with ZrO2, MnO and Fe2O3 was grown from Li-riched melt by Czochralski method. The defect structures and composition of these crystals were analyzed by means of ultraviolet-visible and infrared transmittance spectra. The appearance of 3466 cm-1 peak in infrared spectra showed that the crystal grown from Li-riched melt was near stoichiometric. The photorefractive properties at the wavelength of 488 nm and 633 nm were investigated with two-beam coupling experiment, respectively. The experimental results showed that the response speed and sensitivity were enhanced significantly and the high diffraction efficiency was obtained at 488 nm wavelength. This manifested that near-stoichiometric LiNbO3:Mn:Fe:Zr crystal was an excellent candidate for holographic storage. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
    Crystal Research and Technology 11/2010; 45(11):1123 - 1126. DOI:10.1002/crat.201000383 · 0.94 Impact Factor
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    ABSTRACT: The ultraviolet (UV) band edge photorefractivity of Sn-doped LiNbO(3) (LN:Sn) at 325 nm has been investigated. A sharp decrease of beam distortion, which is accompanied by a significant increase in the photoconductivity, is observed in LN:Sn crystals with Sn-doping concentrations at or above 2.0 mol%. The diffraction efficiency, the holographic recording sensitivity and response rate, and the two-wave coupling gain coefficient are greatly enhanced when the Sn-doping concentration reaches 2.0 mol% or more. Unlike LiNbO(3) doped with Hf in which the UV gratings can be erased easily by a red beam, the UV gratings in LN:Sn can withstand long-term red beam illumination. Electrons are determined to be the dominant light-induced charge carriers responsible for the UV band edge photorefraction. The observed enhancement on the UV band edge photorefractivity is found to be associated with the showup of an absorption band around 325 nm in LN:Sn crystals with Sn-doping concentrations at or above 2.0 mol%.
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