Open AccessRotational Doppler effect by space-time-coding metasurfaces for nonreciprocal electromagnetic isolation
Author(s) -
Baiyang Liu,
SaiWai Wong,
Luqiao Yin
Publication year - 2021
Publication title -
optics express
Language(s) - Uncategorized
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.432886
Subject(s) - optics , physics , doppler effect , electromagnetic radiation , wavefront , angular momentum , astronomy , quantum mechanics
Metasurfaces are artificial structures that can arbitrarily manipulate electromagnetic (EM) wavefronts. We propose a nonreciprocal EM isolating surface based on space-time-coding metasurfaces that generates orbital angular momentum (OAM)-carrying beams with electronic rotational Doppler effect. The region between two parallel 1-bit programmable space-time-coding OAM metasurfaces, one each for frequency and OAM order up-conversion and down-conversion, induce rotational Doppler shifts from opposing incident directions. An intermediate frequency-selective surface with highpass characteristics transmits the up-conversion signals and blocks the down-conversion signals. Hence, the EM waves are sensitive to illumination direction, exhibiting EM isolation responses, and the incident waves are only transmitted unidirectionally.