Quantum Theory of Surface Polaritons in Semi–Infinite Dielectric Systems11The project supported by National Natural Science Foundation of China through grant No. 68977017 and9687006-01.

Abstract

The interaction system of a semi-infinite diatomic dielectric and the electromagnetic field propagating parallelly to the surface is studied. The long–wave optical phonon modes of the semi–infinite dielectric are calculated including the electronic polarizability by a quantum–mechanical theory. Retardation effects are neglected. A quantum field theory method of surface polaritons is developed to calculate the operator describing the interaction between a photon and the phonon polarization fields of the semi–infinite crystal, with explicit inclusion of surface effects. The dispersion relations of the surface phonon–polaritons are derived and discussed. The results are in good agreement with those obtained by the conventional, macroscopic dielectric theory of surface polaritons and experimental ATR (attenuated total reflection) spectra. The dispersion curves of polariton leaking modes caused by the interaction between bulk TO mode with surface effect and photons are presented in a graphical form. The –dependence of the electric field strength in each polariton branch is calculated and presented also in a graphical form. We also research the spatial dependence of the field strength in each polariton branch. It is found that these properties are influenced and modulated by the surface phonons because of the interaction between photons and the surface phonon modes of the semi-infinite dielectric system. Hence the divergent nature (diffraction effect) of light propagating along the fibers and waveguides is restrained. We present a method how to use the boundary conditions in the quantum theory, which will be discussed in detail.