Near field phenomena in dipole radiation
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Author
Xu, Zhangjin
Item Type
DissertationAdvisor
Arnoldus, Henk F.Committee
Wang, ChujiPierce, Donna M.
Pradhan, Prabhakar
Koshka, Yaroslav
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Abstract
In this dissertation we have studied near-field phenomena in dipole radiation.
We have studied first the energy flow patterns of the radiation emitted by an electric dipole
located in between parallel mirrors. The field lines of the Poynting vector have intricate structures,
including many singularities and vortices. For a dipole parallel to the mirror surfaces, vortices
appear close to the dipole. Vortices are located where the magnetic field vanishes. Also, a radiating
electric dipole near the joint of two orthogonal mirrors is considered, and also here we find
numerous singularities and vortices in the energy flow patterns. We have also studied the current
density in the mirrors.
Next we have studied the reflection of radiation by and the transmission of radiation
through an interface with an -near-zero (ENZ) material. For p polarization, we find that the
reflection coefficient is -1, and the transmission coefficient is zero for all angles of incidence. The
transmitted electric field is evanescent and circularly polarized. The transmitted magnetic field is
identically zero. For s polarization, the transmitted electric field is s polarized and the transmitted
magnetic field is circularly polarized.
The next topic was the study of the force exerted on the dipole by its own reflected field near an ENZ interface. We found that, under certain circumstances, it could be possible that the dipole would levitate in its reflected field. This levitation is brought about by evanescent reflected waves.
Finally, power emission by an electric dipole near an interface was considered. We have derived expressions for the emitted power crossing an interface. The power splits in contributions from traveling and evanescent incident waves. We found that for an ENZ interface, only evanescent dipole waves penetrate the material, but there is no net power flow into the material.