Tunable Undirectional Excitation And Bfocusing Properties Of SPPs Based On V-Shaped Magnetic Antennas

Magnetic antennas is one of many optical nanoantennas. Optical nanoantennas generally refer to devices made up of metal nanostructures with different shapes to convert freely propagating optical radiation into localized energy, and vice versa. It has been research focus because of its unique characteristics such as field enhancement, local field effect and field redirection. Better antennas with higher coupling efficiency, higher splitting ratio can be achieved through designing its structure. Furthermore, it is promising in those aspects such as the near-field optical microscopy, single photon emitters, polarization detection, optical tweezers and sensors, etc. Here we made detailed analysis and research on the SPPs excitation features of V-shaped magnetic antennas.When illuminated by light with different states of polarization, the excitation characteristics of V-shaped magnetic antennas were discussed by the finite element method. Field distribution on both sides were given in accordance with dipole model, and unidirectional excitation conditions of SPPs were maintained afterwards. According to the numerical simulation results, we got the polarization state of incident light which can achieve absolute unidirectional excitation and the excitation features of circular polarization.Based on V-shaped magnetic antennas, we projected two arrangement modes of V-shaped magnetic antennas, which were circular array and Archimedes spiral array, respectively. By introducing vector beam and changing coefficient of Archimedes spiral, high efficiency centre focusing were maintained. After analyzing the relations between coupling light intensity of V-shaped magnetic antennas and stokes parameter of incident light, the structure of V-shaped magnetic antennas can be arranged to measure every component of stock parameter. In short, we noted that this structure, can be a practical way of polarization detection scheme.