Non-reciprocal devices enabled by metamaterials

Advances in non-reciprocal devices enabled by metamaterials are presented. In particular, a compact polarization-independent isolator is proposed based on metasurfaces with modulated periodicity, which may provide similar functionality as conventional polarizing beam-splitters (PBSs) based on uniaxial crystals but with dimensions many orders of magnitude smaller. Furthermore, direction-selective non-reciprocal devices, such as isolators and Faraday rotators, are introduced by placing magneto-optical (MO) slabs in between epsilon-near-zero (ENZ) materials. Finally, a new class of sub-wavelength nonlinear magnetic-free isolators is proposed, consisting of a non-linear band-stop metasurface and a linear bandpass one at the opposite sides of a quarter-wavelength slab.