In this paper a new design of the electrooptic light modulator is proposed, which uses the diffraction of a laser beam caused by the periodic skin field behind a electroded surface of an electrooptic crystal at the moment of the total internal reflection. Interdigital modulation electrodes are attached to they-zsurface of a LiTaO3single crystal. The number of electrode pairs per unit length, the width of a single electrode, and the effective area are 4800 m-1, 20μm, and 50 mm2, respectively. The effective full-modulation voltage and the capacitance between the opposite readout of the modulator were measured to be 18 V and 44 pF, respectively. These values are proved to be in good agreement with those obtained by the theoretical estimations. At the Gaussian limit case a design of the modulator under a restricted driving power requirement is also indicated.