Sorting polarized photons with a single scatterer

Abstract: Intuitively, light impinging on a spatially symmetric object will be scattered symmetrically. This intuition can fail at the nanoscale if the polarization of the incoming light is properly tailored. In fact, it has been demonstrated that near-field interference can result in the unidirectional excitation of plasmonic modes using circularly polarized light. Here we show that linearly-polarized photons impinging on a single spatially-symmetric scatterer created in a silicon waveguide are guided into a certain direction of the waveguide depending exclusively on their polarization angle. Reciprocity implies that the scatterer can also act as a two-input dielectric nanoantenna radiating two different linear polarizations. Our work broadens the scope of near-field interference beyond plasmonics, with applications in polarization (de)multiplexing, unidirectional coupling, directional switching, radiation polarization control, and polarization-encoded quantum information processing in photonic integrated circuits.