Transmission of Electromagnetic Waves through a Subwavelength Slit using a Reconfigurable Phase-Gradient Metasurface

In the past two decades, light beaming through subwavelength apertures surrounded by grating structures have attracted extensive research interests. In this study, we propose a method to achieve on-axis beaming of electromagnetic waves diffracted by a subwavelength slit using a phase-gradient metasurface. Near-field distributions from both numerical simulations and experimental measurements are presented. The beaming phenomenon is further maintained over a non-negligible frequency bandwidth from 9 GHz to 12 GHz by modulating the phase profile of the metasurface through varactor diodes inserted in the constituting unit cells.