Shared-aperture full-duplex Janus meta-lens for asymmetric focusing of electromagnetic waves

Janus metasurfaces have provided a platform for multiplexing diverse electromagnetic (EM) wave functionalities, which are determined by the intrinsic propagation direction of the EM wave. However, most existing approaches only utilize half of the metasurface aperture for each EM functionality. Here, we propose a method that employs receiver–transmitter Janus meta-atom to accomplish high-efficiency transmission and asymmetric phase responses. By fully implementing the direction-duplex strategy through these meta-atoms, we can directly assign asymmetric phase profiles to the Janus meta-lens in order to achieve a direction-selective focusing configuration, thereby effectively improving aperture utilization. Experimental validation is conducted in the microwave region to demonstrate the feasibility of the proposed method, showcasing potential applications of shared-aperture Janus metasurfaces in asymmetric imaging and multichannel information processing.