Oblique Incidence of an Electromagnetic Wave on a Plane-Parallel Dielectric Plate

Using electrodynamic analysis of the 3D model of a plane-parallel ideal dielectric plate, the propagation of plane linearly polarized electromagnetic waves is investigated in the case when their angle of incidence φ deviates from the normal to the plane of the plate. It is found that in the case of parallel polarization, when the electric field vector lies in the plane of incidence and magnetic field vector is parallel to the plane of plate, the Q factor of the observed half-wave resonance first decreases to its minimal value with increasing φ as the Brewster angle is approached, and then increases, tending to infinity as φ → 90°. In the case of perpendicular polarization, when the magnetic field vector lies in the plane of incidence and the electric field vector is parallel to the plane of the plate, the Q factor of the half-wave resonance gradually increases with increasing φ, also tending to infinity as φ → 90°. However, the dependences of the observed monotonic increase in the resonance frequencies with the angle of incidence are identical for both polarizations. The results of experiment with a plane-parallel plate made of ultrahigh molecular weight polyethylene with a dielectric constant of 2.5, which has been performed using broadband horn antennas, are in good agreement with the results of the electrodynamic calculation based on the 3D model.