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: 2.21). 03/2010; DOI: 10.1063/1.3305339
Source: IEEE Xplore

ABSTRACT 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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