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An analytical formulation has been developed for the shielding effectiveness of a rectangular enclosure with an aperture. Both the magnetic and electric shielding may be calculated as a function of frequency, enclosure dimensions, aperture dimensions and position within the enclosure. Theoretical values of shielding effectiveness are in good agreement with measurements. The theory has been extended to account for circular apertures, multiple apertures, and the effect of the enclosure contents.

The progress, and current challenges, in fabricating rare-earth-doped chalcogenide-glass fibers for developing mid-infrared (IR) fiber lasers are reviewed. For the first time a coherent explanation is forwarded for the failure to date to develop a gallium-lanthanum-sulfide glass mid-IR fiber laser. For the more covalent chalcogenide glasses, the importance of optimizing the glass host and glass processing routes in order to minimize non-radiative decay and to avoid rare earth ion clustering and glass devitrification is discussed. For the first time a new idea is explored to explain an additional method of non-radiative depopulation of the excited state in the mid-IR that has not been properly recognized before: that of impurity multiphonon relaxation. Practical characterization of candidate selenide glasses is presented. Potential applications of mid-infrared fiber lasers are suggested.

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A fast and accurate method is developed to compute the natural frequencies and scattering characteristics of arbitrary-shape two-dimensional dielectric resonators. The problem is formulated in terms of a uniquely solvable set of second-kind boundary integral equations and discretized by the Galerkin method with angular exponents as global test and trial functions. The log-singular term is extracted from one of the kernels, and closed-form expressions are derived for the main parts of all the integral operators. The resulting discrete scheme has a very high convergence rate. The method is used in the simulation of several optical microcavities for modern dense wavelength-division-multiplexed systems.

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