Morphology-dependent resonances of a dielectric sphere on a conducting plane

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Abstract
A theoretical treatment of the morphology-dependent resonances of a dielectric sphere on or near a plane surface of infinite conductivity is presented. The scattering theory for this problem is reviewed, and computational procedures are described. Resonance peaks are identified and correlated with the corresponding resonances in the isolated sphere. The study examines how the locations and widths of the resonances change as the particle approaches the surface. The locations of the TE resonances (expressed as size parameter) shift to higher values, the locations of the TM resonances shift to a lower values, and the widths are broadened. As the particle approaches the surface, 90% of the change in location occurs within a distance of ~ 0.1 of a particle radius from the surface. The reason for this behavior is discussed. An example case is presented that shows how a narrow resonance that is completely suppressed by internal losses in an isolated sphere can become an active and strong resonance when the sphere is brought near a conducting surface.