Higher Efficiency Plasmonic Vortex Based on Transmissive Multi-Arm Archimedes Spiral Structures with Asymmetric Nano-Slits

In this paper we proposed and investigated a higher efficiency plasmonic vortex by adding an auxiliary nanogroove in the multi-arm Archimedes spiral slit; the added nanogroove helps enhance the intensity of the generated plasmonic vortex using transmissive spiral structures to help position the incident and reflected beams on opposite sides of the metal structure, which reduces background noise interference from the incident light. In addition, the proposed structures can generate plasmonic vortex with different orders when illuminated with circularly polarized light. When illuminated with circularly polarized light, the relative peak intensity of the primary ring electric field formed outside the central dark field reaches up to 1.45 times that without auxiliary metal groove and when illuminated with linearly polarized light, this intensity ratio reaches up to 1.42 times. Therefore, the background noise can be reduced. The proposed structure is helpful for the high-density integration of optical chips, holding significant implications for advancing the miniaturization and integration of future optoelectronic devices.