In this contribution, we propose a magnet-less non-reciprocal isolating system based on time-varying metasurfaces. The system consists of a conventional frequency selective device placed between two time-varying metasurfaces, one for frequency up-conversion and one for down-conversion by the same amount. The overall reciprocity of the system is broken by exploiting the different scattering response from the embedded device when illuminated from opposite directions, since the two time-varying metasurface imparts an opposite frequency conversion for the two directions of illumination, but the transmitted fields are always the same as for the incident one, since the metasurfaces vanish the frequency conversion of each other. This strategy can be successfully exploited for conceiving a new family of non-reciprocal isolating systems starting from any conventional electromagnetic device.
Ramaccia, D., Sounas, D.L., Marini, A., Toscano, A., & Bilotti, F. (2020). Achieving electromagnetic isolation by using up- and down-converting time-varying metasurfaces. In 2020 14th International Congress on Artificial Materials for Novel Wave Phenomena, Metamaterials 2020 (pp.1-2). Institute of Electrical and Electronics Engineers Inc. [10.1109/Metamaterials49557.2020.9285032].