Transistor-Loaded Nonmagnetic Nonreciprocal Metasurfaces

Reciprocal metasurfaces represent prominent compact structures for bidirectional and frequency-invariant transformation of electromagnetic waves. However, their application to modern wireless communication are limited due to their reciprocal response and lack of a controllable, versatile and programmable mechanism. On the other hand. nonreciprocal metasurfaces are capable of steering electromagnetic waves unidirectionally, leading to functionalities that are far beyond the capabilities of conventional static metasurfaces. In addition, they are controllable and programmable through their active constituents. This paper provides an overview on recent progress and opportunities offered by transistor-loaded metasurfaces to break reciprocity, and discusses their potential for low-energy, compact, and integrated nonreciprocal devices and systems.