Catenary Electromagnetics for Ultra-Broadband Lightweight Absorbers and Large-Scale Flat Antennas.

Catenary functions are exciting and fundamental building blocks in constructing various kinds of waves in subwavelength structures. Here, a simple yet powerful approach inspired by catenary optics is proposed to realize efficient manipulation of electromagnetic waves in terms of both amplitude and phase. By properly engineering the catenary electromagnetic fields and frequency dispersion, lightweight metafilm-based broadband absorbers with polarization-independent bandwidth covering 0.65-6.2 GHz are experimentally achieved, and the bandwidth is further broadened to 0.9-40 GHz. With the same approach, a large-scale flat antenna based on generalized reflection is demonstrated in the satellite communication system. To enable the batch manufacturing, a flexible substrate-based microfabrication process is developed with a minimum feature size of down to sub-micrometer and total size up to almost 1 m. These results may provide important guidance for the design of metasurface-based devices.