PROPAGATION OF ELECTROMAGNETIC WAVES ALONG DIELECTRIC INTERFACE

Abstract

Investigation of electromagnetic waves propagating along plane dielectric interface poses a very interesting and challenging problem. It is known that the phase velocities of the electromagnetic waves in dielectric media depend on the constitutive parameters of the media. Although phase velocities of electromagnetic waves in different dielectric media are different the tangent.ial elect.ric and magnetic field~ across the interface mu~t be continuous t.o satisfy the boundary conditions. The studies carried out so far in t.he field of propagation along dielectric interface show discontinuous t.angential field components across the int.erface thereby violating boundary condit.ions. The discontinuity exists in the phase and hence in the phase velocity of the field components whereas the magnitude is continuous acro~s the interface. It i~ desired to find such a ~olution for which phase as well as magnitude of field component~, E and if are continuous across the interface thereby satisfying Maxwell's equations. To study the propagation behavior along the interface two classes of problems have been considered. In the first class of problems current sources of finite extent have been considered and in the second clas~ the source considered is an infinite current sheet. In the first class of problems electric field due to electric currents source parallel to the interface was investigated. The first order asymptotic evaluation of field components shows a null of the electric field at the interface. This solution satisfies the continuity of electric field while the magnetic field component is discontinuous. Higher order asymptotic evaluations have been employed to get further insight into this propagation problem. The results show that the wavefronts need not be discontinuous. In the second class of problems a current sheet was 8.'3sumed to be present across the interface to see the behavior of plane wave near the dielectric interface due to an infinite source. Among various source configurat.ions considered in this work' the continuity of the pha.se front.s is found to be preserved with the help of interesting and stable structures of phase fronts. These structures are formed by two types of critical points in the phase map known as saddle points and center points. The phase map plots show that these points exist. near t.he interface in bot.h half spaces when· finit.e extent sources are present. While t.he infinite extent source was responsible for creation of these points in the upper half space only . These points are located periodically along the interface while their position above or below the interface depends upon the refractive index of the denser medium of the two dielectric half spaces. It was found that the refractive index also effects the periodicity of these points along the interface.