Lateral displacement and distortion of beams incident upon a transmitting-layer configuration

The field resulting from a beam incident upon a planar dielectric layer placed between media having different refractive indices is examined by using both an approximate approach and a highly accurate Gaussian-beam analysis. We find that, if the incidence angle is adjusted to couple energy to a leaky wave that may be guided by the layer, both the reflected and the transmitted beams may undergo large lateral displacements. The transmitted beam is then always shifted in a forward direction, but the displacement of the reflected beam can be either forward or backward. We show that these effects are produced by distortion of the beam profiles caused by the leaky-wave coupling mechanism, which accounts for lateral shifts of the beam axes. The possible presence of absorption loss in the layer is also considered, and we find that the reflected beam may be effectively suppressed under certain critical combinations of the physical parameters involved.