Penrose Super-Radiance in a Synthetically Rotating Metasurface

Super-radiant amplification of scattering in a rotating medium was predicted by Sir Penrose as an exotic astrophysics phenomenon. Here we demonstrate its electromagnetic analogue using spatio-temporally modulated metasurfaces that experience a form of synthetic rotation. We consider excitations with signals carrying orbital angular momentum (OAM), highly beneficial for multiplexed wireless networks that demand high data rate capacity. The metasurface efficiently couples and can amplify selected OAM orders based on a phenomenon analogous to Penrose super-radiance. We build, analyze, and simulate a single circuit element, modulated in time through varactors, that efficiently manipulates three OAM orders and selectively amplifies them. We then show the possibility of observing angular Doppler shift and amplifying selected OAM signals using an array of these elements forming a metasurface.