Irregular elliptical plasmonic rings for engineering near-field and phase

The near-field and phase distribution patterns of surface plasmon polaritons excited on different types of irregular elliptical rings are investigated with respect to linear and circular polarized lightwave. It is interestingly found that under linear polarization, the rings exhibit the dipole-like field and phase patterns, while under circular polarization they provide the omnidirectional vortex field and phase patterns. The field patterns produced by different rings demonstrated different shapes and amplitudes. The reason is due to different phase-matching conditions, which arise from internal geometrical variations of elliptical rings. These specified phase and near-field manipulations are of high potential for many applications such as optical trapping and beam shaping.