Theory and Development of Near-Field Plates
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The widespread use of the electromagnetic near field, in applications ranging from high resolution imaging devices to wireless power transfer systems, has called for focusing devices with higher resolutions and larger focal lengths. This demand, however, faces a major obstacle: the diffraction limit. Due to this limit, subwavelength resolutions are only possible at near-field distances.
A novel solution is proposed for overcoming the diffraction limit: near-field plates (NFPs). NFPs are non-periodically patterned surfaces that can form desired subwavelength patterns at specified near-field distances. They are simple to fabricate, robust to inherent losses, and allow the near field pattern to be stipulated. Given these advantages, they show great promise as a simple and effective method for tailoring the electromagnetic near field. In this thesis, the first reported NFP is introduced and its operation is analytically studied. The NFP concept is then advanced through several phases, addressing a major issue in each phase. NFPs suitable for practical applications are introduced, and their design and operation are described. Their ability to tailor the electromagnetic near field is verified through full-wave simulations and experiments. Finally, application areas of NFPs such as near-field probing and imaging, biomedical devices, and wireless power transfer systems are discussed.