All-metallic geometric metasurfaces for broadband and high-efficiency wavefront manipulation

Geometric metasurfaces have shown superior phase control capacity owing to the geometric nature of their phase profile. The existing geometric metasurfaces are generally composed of metal-dielectric composites or all-dielectric subwavelength structures. Here, a novel configuration, all-metallic structure, is proposed to achieve broadband and high-performance electromagnetic wave-front manipulation based on the geometric phase. A catenary model is built to describe the optical dispersion and guide the design of metasurfaces. Two metadevices including a beam deflector and a hologram are designed and experimentally demonstrated in the infrared regime, with the measured optical efficiency up to 84% (the simulated efficiency reaches 93%). Compared to previous metal-insulator-metal structures, this approach can realize higher efficiency and broader operating bandwidth owing to its lower ohmic loss. This design strategy is universal and can be easily scaled to any other spectra without complex optimization. Moreover, since metals have excellent mechanical and physical properties, such as good thermal and electrical conductivity, this all-metallic structure may provide a new thinking on interdisciplinary research.