Photoinduced conductivity during sub-bandgap illumination in periodically poled MgO:LiNbO3 with charged domain walls

Abstract

We report observations of a spectral dependence of the conductivity in 5 mol.% MgO doped LiNbO3 single crystals with periodical domain structure (PDS) of stripe domains with charged domain walls during sub-bandgap illumination by probing laser beams. The photoinduced conductivity is manifested through a comparatively slow relaxation of the first-order Bragg electrooptical diffraction efficiency after application of an external electric field to the crystal. The relaxation rate connected with screening of the external field due to redistribution of the space charge over the conductive charged domain walls linearly increased in the initial stage with the probe beam intensity. The parameters of the effective photoinduced conductivity averaged over the PDS period that describe its dependence on the intensity decreased from 10.9⋅10−14 to 1.79⋅10−16 Ω−1W−1m as the wavelength of the probe beam increased from 457 to 980 nm.