We theoretically investigate the surface structure of a photorefractive grating that is formed with the use of a bulk interference pattern by photovoltaic effect in X-cut lithium niobate crystal short-circuited along <i>z</i>-axis. The steady-state gratings with the wave vector directed along the <i>z</i>-axis in the samples with dielectric and metallized (shortcircuited) <i>x</i>-boundaries are considered. The amplitude of the surface relief grating in the sample with metallized boundary exceeds one for the case of dielectric boundary. The existence near such metallized surface the <i>x</i>-component of electric space-charge field causes here the predominance of perturbation for off-diagonal component <i>?B</i>
<sub>31</sub> of the dielectric impermeability tensor at optical frequency.
© 2005 Optical Society of America