Nonreciprocal Metasurfaces with Epsilon-Near-Zero Materials
Albert Mathew, Rebecca Aschwanden, A. Tripathi, Piyush Jangid, Basudeb Sain, Thomas Zentgraf, Sergey Kruk
Abstract
Nonreciprocal optics enables the asymmetric transmission of light when its sources and detectors are exchanged. A canonical example─optical isolator─enables light propagation in only one direction, similar to how electrical diodes enable unidirectional flow of electric current. Nonreciprocal optics today, unlike nonreciprocal electronics, remains bulky. Recently, nonlinear metasurfaces opened a pathway to strong optical nonreciprocity on the nanoscale. However, demonstrations to date were based on optically slow nonlinearities involving thermal effects or phase transition materials. In this work, we demonstrate a nonreciprocal metasurface with an ultrafast optical response based on indium tin oxide in its epsilon-near-zero regime. It operates in the spectral range of 1200–1300 nm with incident power densities of 40–70 GW/cm 2 . Furthermore, the nonreciprocity of the metasurface extends to both amplitude and phase of the forward/backward transmission, opening a pathway to nonreciprocal wavefront control at the nanoscale.