Propagation properties of a light wave in a film quasiwaveguide structure

Abstract

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.

Determination of refractive index, thickness, and the optical losses of thin films from prism-film coupling measurements

“…For all these applications, it is necessary to perform an accurate characterization of the optical properties, which include refractive index and optical losses. The optical losses of a thin film have three different origins: surface scattering due to the surface roughness, volume scattering due to volume defects such as inhomogeneity, and volume absorption due to intrinsic absorption [1,2]. From a practical point of view, this characteristic is of particular importance since it can severely degrade or modify the performances of a component.…”

A method to retrieve optical and geometrical characteristics of three layer waveguides from m-lines measurements

“…Indeed, the broad peaks correspond to the waves guided in the PZT layer only, while the narrow peaks are associated to the waves also guided in the ZnO. This broadening is not a peculiarity of the three layer structure, it can be also observed for PZT single layers and may be due to light diffusion resulting in a loss along the direction of propagation [14]. The transition from the two guiding layer regime to the three guiding layer regime can not be infered from the spectrum and has to be determined by numerical computation.…”

“…We call this structure a "three layer waveguide", whereas in the nomenclature of other authors [10] it would be called a "5 layer waveguide". The central layer (layer #2) is the core of the structure and the layers #1 and #3 are the claddings (true waveguide [14]). As a consequence, we assume for the refractive indices of the different layers that:…”

A method to retrieve optical and geometrical characteristics of three layer waveguides from m-lines measurements

“…Indeed, the broad peaks correspond to the waves guided in the PZT layer only, while the narrow peaks are associated to the waves also guided in the ZnO. This broadening is not a peculiarity of the three layer structure, it can be also observed for PZT single layers and may be due to light diffusion resulting in a loss along the direction of propagation [14].…”