Circularly and elliptically polarized near-field radiation from nanoscale subwavelength apertures

With advances in nanotechnology, obtaining circularly and elliptically polarized optical spots beyond the diffraction limit is an emerging need for plasmonic applications. Two techniques are suggested to obtain circularly and elliptically polarized near-field radiation using subwavelength apertures. It is demonstrated that a square aperture can mediate diffraction limited circularly or elliptically polarized radiation into an optical spot with circular or elliptical polarization beyond the diffraction limit. Linearly polarized diffraction limited radiation is converted into a circularly or an elliptically polarized optical spot beyond the diffraction limit by creating asymmetry in the subwavelength aperture.