The peculiarities of the director and polarization gratings recorded due to light-induced anchoring effect in liquid crystal media doped with azo-dye were found and studied. Depending on the ratio of the grating period to the cell's thickness, either asymmetrical LC director distribution or quasi-sinusoidal director modulation were formed. The observed behavior can be explained in terms of surface and bulk interaction of twist domains presenting the grating stripes. We showed the possibility to control the grating diffraction efficiency by applying the ac electric field, increasing the diffraction efficiency up to 30%.