Spin-orbit-enabled sorting of optical flows in plasmonic nanocircuits.

On-chip controlling of photon spin is essential in developing future integrated nanophotonics with complex functionalities. Here we propose and demonstrate a robust spin-sorting nanocircuit, which consists of a spin-orbit coupler (i.e., combined nanoring and nanodisk) and an L-shaped dielectric-loaded surface plasmon (DLSPs) waveguide. The nanocircuit with optimized geometric parameters is shown to be capable of unidirectionally exciting and routing a DLSP mode along an independent waveguide. We found experimentally that the proposed device possesses an average insertion loss (extinction ratio) of 0.13 dB (14.8 dB) under complete circularly polarized incidence with opposite spin, which is in good agreement with theoretical calculations. The proposed spin-selective scheme may pave the way for applications in the manipulation of chirality with a flexible degree of freedom.