Transmission of electric dipole radiation through an interface |
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Authors: | Henk F Arnoldus Matthew J Berg Xin Li |
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Institution: | 1. Department of Physics and Astronomy, Mississippi State University, P.O. Drawer 5167, Mississippi State, MS 39762-5167, USA;2. Department of Physics, P.O. Box 1002, Millersville University, Millersville, PA 17551, USA |
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Abstract: | We consider the transmission of electric dipole radiation through an interface between two dielectrics, for the case of a vertical dipole. Energy flows along the field lines of the Poynting vector, and in the optical near field these field lines are curves (as opposed to optical rays). When the radiation passes through the interface into a thicker medium, the field lines bend to the normal (as rays do), but the transmission angle is not related to the angle of incidence. The redirection of the radiation at the interface is determined by the angle dependence of the transmission coefficient. This near-field redistribution is responsible for the far-field angular power pattern. When the transmission medium is thinner than the embedding medium of the dipole, some energy flows back and forth through the interface in an oscillating fashion. In each area where field lines dip below the interface, an optical vortex appears just above the interface. The centers of these vortices are concentric singular circles around the dipole axis. |
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Keywords: | Reflection Transmission Poynting vector Optical vortex Angular spectrum Fresnel coefficients Dipole radiation |
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