Optimization of Aperture Antenna with V-groove Structures to Improve Intensity of Nanosized Circularly Polarized Light

We numerically demonstrated that strong nanosized circularly polarized light (CPL) could be obtained using aperture antennas with three, four and five V-groove structures, due to the strong intensity enhancement effect of channel plasmon polaritons generated in the V-groove structures. Simulation results based on finite element method revealed that CPL with intensity enhancements of 8900, 22700 and 22875 times could be obtained by aperture antennas with three, four and five V-groove structures, respectively. As expected, the intensity enhancement of the CPL increased with the number of the V-groove structures. However, the intensity enhancement seemed to become saturated by just increasing the number of the V-groove structures. From a practical point of view, we considered that the aperture antenna with four V-groove structures was the best structure to obtain strong nanosized CPL, because it was more difficult to fabricate aperture antennas with three, five or more V-groove structures. Moreover, the dependences of groove length and groove angle were investigated to obtain greater intensity enhancement of CPL. As a result, CPL with greater intensity enhancement could be obtained using aperture antenna with V-groove structures for short groove length and large groove angle. We also investigated the dependence of wavelength of incident light, and found that the aperture antenna with V-groove structures could function over a wide wavelength range from 580 nm to 960 nm. The aperture antenna with V-groove structure could be used to investigate the spin-relate phenomena in nano-regions.