Bifunctional Integration Performed by a Broadband High‐Efficiency Spin‐Decoupled Metasurface

Abstract Achieving broadband multitasked integration on an ultrathin interface is pivotal to increasing data capacity. However, broadband bifunctional metasurfaces exhibiting high‐efficiency and crosstalk‐free characteristics are rarely seen. Here, three broadband spin‐decoupled criteria are developed to design the meta‐atoms of high‐efficiency bifunctional metasurfaces. Specifically, six dipole‐loaded quasi‐I‐shaped meta‐atoms are proposed to satisfy the broadband spin‐decoupled criteria in radio band from 8.6 to 17.8 GHz (about 70% bandwidth) with more than 90% efficiency. The metasurface equipped with the proposed meta‐atoms can keep dispersionless phase gradients and crosstalk‐free characteristics in two orthogonal circular polarizations. This work demonstrates the broadband scheme with spin‐decoupled bifunctional metasurface, yielding two independent broadband multimode vortex beams in two completely decoupled helicities. Besides, other possible applications of the proposed meta‐atoms are illustrated from the perspective of the half‐wave plant (polarization control). Accordingly, the other multitasked‐type bifunctional metasurface is fabricated to achieve the broadband integration of two different functionalities: polarization conversion and full‐polarization anomalous refraction. The proposed schemes offer broadband, polarization‐multiplexing, and multitasked‐integration routes for complex electromagnetic wave manipulations within a subwavelength thickness, which can stimulate the development of electromagnetic/optical integration devices with broadband multiplexing techniques.