A self-biased non-reciprocal magnetic metasurface for bidirectional phase modulation

Abstract

Non-reciprocal metasurfaces can encode optical functions on forward- and backward-propagating waves, and could be used to create non-reciprocal antennas and radomes for full-duplex wireless communication and radar systems. However, such metasurfaces typically require external electric- or magnetic-field biasing or rely on non-linear effects, which makes practical implementation challenging. Here we report a self-biased non-reciprocal metasurface based on magnetic meta-atoms made from lanthanum-doped barium hexaferrite. The metasurface offers a transmittance of up to 77% and an operation angle of ±64°. We show that they can be used for on-demand bidirectional phase modulation, which provides non-reciprocal functionalities including microwave isolation, non-reciprocal beam steering, non-reciprocal focusing and non-reciprocal holography. The approach could also be potentially extended to megahertz and optical frequencies by using different self-biased magnetic materials.