Analysis of dielectric-loaded cavities using an orthonormal-basis method

An orthonormal-basis method to analyze dielectric-loaded cavities is proposed. Resonant frequencies and fields are obtained by solving an eigenvalue problem in which the modes of an auxiliary problem define the orthonormal-basis that is used to expand the fields of the original problem. The merit of our approach is to take advantage of some mathematical properties to develop a computationally efficient and versatile method. The accuracy of the method is demonstrated by comparing our results with other results available in the literature.     

Analysis of inhomogeneously dielectric filled cavities coupled to dielectric-loaded waveguides: application to the study of NRD-guide components

In this paper, we present two contributions. First, we develop a computationally efficient technique for the full-wave characterization of inhomogeneously dielectric-filled cavities connected to inhomogeneously dielectric-loaded waveguides. This method is based on the expansion of the electromagnetic field within the cavity in terms of their solenoidal and irrotational modes. The presented formulation allows the treatment of hybrid modes in the waveguide ports, where the definition of a characteristic modal impedance or admittance is not possible. The multimode scattering matrix of the structure is computed throughout an efficient implementation of the orthonormal-basis method for the calculation of the cavity modes. Secondly, we have employed the present technique for the analysis and design of nonradiative dielectric (NRD) guide components and discontinuities. Moreover, the application of the bi-orthonormal-basis method for the calculation of the full-spectrum of NRD guides is demonstrated as being a very efficient approach for the rigorous treatment of such guides. Next, an efficient computer-aided design tool has been developed for the analysis of complex NRD-guide circuits. We have compared our simulations with theoretical and experimental results available in the technical literature, fully validating our software. This code has been employed for the specific analysis of a linear continuous taper to match two NRD guides with different widths, demonstrating a considerable reduction of the return losses over a wide frequency band. Finally, stopband and bandpass NRD-guide filters based on an electromagnetic-bandgap concept are presented.     

Self-similar focusing with generalized devil's lenses

We introduce the generalized devil's lenses (GDLs) as a new family of diffractive kinoform lenses whose structure is based on the generalized Cantor set. The focusing properties of different members of this family are analyzed. It is shown that under plane wave illumination the GDLs give a single main focus surrounded by many subsidiary foci. It is shown that the total number of subsidiary foci is higher than the number of foci corresponding to conventional devil's lenses; however, the self-similar behavior of the axial irradiance is preserved to some extent.     

Spectral anomalies in focused waves of different Fresnel numbers

Light propagation induces remarkable changes in the spectrum of focused diffracted beams. We show that spectral changes take place in the vicinity of phase singularities in the focal region of spatially coherent, polychromatic spherical waves of different Fresnel numbers. Instead of the Debye formulation, we use the Kirchhoff integral to evaluate the focal field accurately. We find that as a result of a decrease in the Fresnel number, some cylindrical spectral switches are geometrically transformed into conical spectral switches.