Toroidal dipole dielectric metasurfaces for mechanically tunable polarization beam splitting

An all-dielectric metasurface composed of high-permittivity ceramic cuboid resonators embedded in polylactic acid is investigated as an angular-dependent polarization beam splitter in the K-band. The operation is based on a strong toroidal resonance with a highly asymmetric Fano profile and the very low (high) dispersion of the associated p-(s-) polarized mode stemming from the particular field profile of the toroidal mode. Large extinction ratios, low insertion losses, and mechanically tunable polarization beam splitting ratio are experimentally demonstrated.