High focusing efficiency plasmonic vortex based on archimedes spiral slot

We proposed an Archimedes spiral slot structure that can achieve plasmonic vortex with high focusing efficiency. By adding an auxiliary slot under the primary spiral slot, the surface plasmon polaritons can be efficiently transmitted in the inward direction, creating a dark spot at the center. Optimization of the geometrical parameters of the spiral slot using the finite-difference time-domain method can achieve unidirectional inward excitation of surface plasmonic polaritons, which improves the focusing efficiency of plasmonic vortex. The structure can reduce background noise, prevent cross-talk of nearby components in the optical networks, further reduce the spacing between integrated devices and improve device integration.