Optical spin waves

Chirality is inherent to a broad range of systems, including solid-state and wave physics. The precession (chiral motion) of electron spins in magnetic materials, forming spin-waves, has shown a wide variety of properties and applications in magnetism and spintronics. We show that an optical analog of spin-waves can be generated in arrays of plasmonic nanohelices. We demonstrate that these optical spin-waves are reflected at the interface between successive domains of enantiomeric nano-helices forming a heterochiral lattice, regardless of the wave propagation direction within the lattice. Optical spin waves may find applications in domains and techniques relying on photon spin, ranging from data processing and storage to quantum optics.