Artificially structured material layers – so-called metasurfaces – may feature exciting optical properties. Such designer surfaces have been utilized for beam-shaping via local manipulation of light fields, for optical sensing, light-routing, spectral filtering, and more. This versatile functionality of metasurfaces is a direct consequence of the underlying working principle, i.e., function-by-structure, a technique brought to perfection by mother nature. The actual optical properties depend on the individual building-blocks (material, geometry, shape, size), the surface is built from, and their relative arrangement.
Metasurfaces also offer the possibility of controlling the flow of light in a flatland scenario by excitation of lattice modes propagating along the structured surface. First discovered by Wood for simple diffractive gratings in 1902, and later interpreted by Rayleigh and Fano, diffractive coupling to electromagnetic waves propagating along the structured layers, usually referred to as Wood or Rayleigh anomalies play an important role also in modern metasurface research.
In the framework of a joint project involving teams from Graz, Monterrey, Ottawa, and Erlangen, it was now demonstrated for the first time that the interaction of light with a metasurface consisting of symmetric nanostructures enables polarization-dependent directional light routing.
The origin of this phenomena is the interplay between symmetric and anti-symmetric modes supported by the individual nanostructures in the artificial metasurface. Even more excitingly, sign and strength of the observed directionality of the lattice modes, and also the out-of-plane diffraction depend sensitively on the incoming polarization, hence representing an ultra-thin optical router, or flatland traffic control. The observed features of the studied system can be realized within a broad wavelength range and open an avenue towards applications in light routing, splitting and control.
Reference:
Mousavi, S., Butt, M. A., Jafari, Z., Reshef, O., Boyd, R. W., Banzer, P., & De Leon, I. (2024). Polarization-controlled unidirectional lattice plasmon modes via a multipolar plasmonic metasurface. Applied Physics Letters, 124(18). https://doi.org/10.1063/5.0195583
Contact:
Peter Banzer; Optics of Nano and Quantum Materials (website)