Switching the angular direction of radiation by the handedness of a circular dipole in the vicinity of a subwavelength Mie scatterer

Abstract

We study the radiation of a circular dipole nearby a subwavelength spherical particle. The circular dipole spins in a plane containing a great circle of the spherical particle (meridional plane). We derive general conditions for which radiation vanishes in any direction lying in the meridional plane, yielding directional radiation whose angular orientation can be changed by switching the handedness of the circular dipole. The radiative response (far field) of this dipole-scatterer system can be synthesized as arising from an effective electric dipole in the meridional plane and an effective magnetic dipole perpendicular to the meridional plane; both dipoles are located at the center of the sphere. We consider a nonabsorbing sphere and explore the radiative characteristics (radiation pattern, directivity, radiated power, and spin angular momentum) in which radiation is nullified along two particular axes lying in the meridional plane; particular geometrical configurations and dielectromagnetic properties of the dipole-scatterer system are given. The directional radiation and spin angular momentum patterns can be rotated $\ensuremath{\pi}\phantom{\rule{0.16em}{0ex}}\mathrm{rad}$ around the axis joining the dipole position and the center of the spherical scatterer by changing the handedness of the circular dipole, excepting for the cases of null radiation in the forward and backward directions. Our work might have implications for transferring quantum spin states to electromagnetic modes, controlling of radiation by emitters, routing of light in networks, manipulating of light propagation with metasurfaces, and sensing and locating molecules.