Negative and Positive Lateral Shift of a Light Beam Reflected from a Grounded Slab

We consider the lateral shift of a light beam reflecting from a dielectric slab backed by a metal. It is found that the lateral shift of the reflected beam can be negative while the intensity of reflected beam is almost equal to the incident one under a certain condition. The explanation for the negativity of the lateral shift is given in terms of the interference of the reflected waves from the two interfaces. It is also shown that the lateral shift can be enhanced or suppressed under some other conditions. The numerical calculation on the lateral shift for a realistic Gaussian-shaped beam confirms our theoretical prediction.