Showing papers on "Coupled mode theory published in 1973"

Coupled-mode theory for guided-wave optics

Abstract: The problem of propagation and interaction of optical radiation in dielectric waveguides is cast in the coupled-mode formalism. This approach is useful for treating problems involving energy exchange between modes. A derivation of the general theory is followed by application to the specific cases of electrooptic modulation, photoelastic and magnetooptic modulation, and optical filtering. Also treated are nonlinear optical applications such as second-harmonic generation in thin films and phase matching.

Coupled mode theory of round optical fibers

Abstract: This paper presents a comprehensive theory of mode coupling in optical fibers with imperfections. The paper begins with the derivation of a general coupled wave theory based on the modes of the ideal fiber. The general theory is applied to a simplified description of guided and radiation modes of the fiber that is valid for small core-cladding index differences. The simplified theory results in expressions for the coupling coefficients that are nearly as simple as those of the slab waveguide. As an example, the theory is applied to the calculation of radiation losses caused by pure core diameter changes and by elliptical deformations of the fiber core.

Coupled-mode theory of unstable resonators

Abstract: Although there has been a sustained interest in unstable open resonators for high-power laser applications, no satisfactory theory has previously been developed to explain the intricate behavior of the complex eigenvalues obtained by numerical solution of the resonator integral equation. The present study proposes a remarkably simple model that predicts the basic features of the published results. In this model, a two-dimensional resonator with finite convex mirrors is regarded as an open-ended waveguide with hyperbolic boundaries. Through use of the modal fields in the waveguide region and modal reflection and coupling coefficients due to the open end, one may construct a resonance equation for the eigenvalues of the free resonant fields (eigenmodes) in the unstable resonator. From a study of the resonance equation as a function of mirror size, it may be concluded that a single waveguide mode is primarily responsible for the eigenmode behavior near a loss minimum, and that two selectively coupled waveguide modes provide the behavior in the intervals between loss minima. The selection of the appropriate waveguide modes is accomplished with the aid of a resonance chart for the simpler problem wherein mode coupling at the open waveguide end is omitted. Results are presented and compared with the earlier literature.

Coupling coefficients for imperfect asymmetric slab waveguides

Abstract: This paper presents a collection of formulas that are necessary for the treatment of radiation and mode conversion phenomena of imperfect asymmetric slab waveguides. The coupled mode theory of dielectric waveguides is briefly reviewed, and general expressions for the coupling coefficients are given. The field expression of the guided and the radiation TE and TM modes of the asymmetric slab waveguide are stated, and are used to derive formulas for the coupling coefficient for slight core boundary irregularities.

Computer analysis of gradually tapered waveguide of arbitrary cross-sections

Abstract: Coupled-mode theory and numerical methods for solving uniform waveguides are combined to analyse the transition of a waveguide of slowly varying arbitrary cross-section. The technique has been applied to the design of the broadband Marie mode transducer. Theoretical and experimental results are given.