Radiation from a dipole perpendicular to the interface between two planar semi-infinite magnetoelectric media

TL;DR

This paper analyzes the radiation pattern of a dipole near an interface between two magnetoelectric media, revealing unique interference and polarization effects caused by axion electrodynamics.

Contribution

It provides an exact Green's function solution and describes novel interference and polarization phenomena in dipole radiation due to magnetoelectric coupling.

Findings

Distinct interference patterns depending on dipole-observer position

Polarization mixing effects absent in standard dipole radiation

Near-interface cylindrical superficial waves influenced by axion electrodynamics

Abstract

We consider two semi-infinite magnetoelectric media with constant dielectric permittivity separated by a planar interface, whose electromagnetic response is described by non-dynamical axion electrodynamics and investigate the radiation of a point-like electric dipole located perpendicularly to the interface. We start from the exact Green's function for the electromagnetic potential, whose far-field approximation is obtained using a modified steepest descent approximation. This procedure yields the standard spherical waves as well as axially symmetric cylindrical superficial waves, which nevertheless are restricted to a region very close to the interface. We compute the angular distribution of the radiation and the total radiated power finding different interference patterns, depending on the relative position dipole-observer, and polarization mixing effects which are all absent in the standard dipole radiation. They are a manifestation of the magnetoelectric effect induced by axion electrodynamics. We illustrate our findings with some numerical estimations employing realistic media as well as some hypothetical choices in order to illuminate the effects of the magnetoelectric coupling which is usually very small.