Propagation properties of a light wave in a film quasiwaveguide structure

We suggest a three-dimensional theoretical model to explain the origin of light wave propagation in a quasiwaveguide structure formed by a thin film of refractive index smaller than the substrate. The physical principles involved are illustrated by the use of a combination of multiple-wave interference and coherent multiple scattering. Not only the theoretical details and the important analytic formulas describing the properties of wave propagation in the quasiwaveguide were given, but also the positions and linewidths of the quasiwaveguide modes, the intensity distribution in the film, the intensity of the reflected spot, and the intensity distribution of the scattered light (m lines) are studied in detail. We divide the modes in the quasiwaveguide into three kinds: cavity modes, leaky modes, and degenerate modes. Some interesting problems are discussed. We investigate the properties of wave propagation in a quasiwaveguide made with a doped polymer film and discuss the origin of scattering. (C) 2002 American Institute of Physics.