High-performance and broadband chirality-dependent absorber based on planar spiral metasurface

A perfect absorber is highly desired in many engineering applications, including cloaking devices and sensor detectors, but most types of absorbers with chirality-dependence have limited bandwidth. In this paper, we propose a novel broadband and chirality-dependent metasurface absorber that consists of an array of planar spiral elements. The spiral orientation can determine the absorption polarization, such as counterclockwise for right circular polarization (RCP) absorption and clockwise for left circular polarization (LCP) absorption. Three steps are adopted to enhance the absorption bandwidth: carefully optimizing the spiral turns, impedance of load resistor, and introducing a matching layer. To demonstrate our concept, we have designed and fabricated a realistic metasurface absorber. The numerical simulations are in good agreement with the experimental results. The simulation and measurement results demonstrate that this device can achieve a broadband (8.3-18 GHz) absorption for RCP incidence, while reflecting the LCP incident waves between 9 GHz to 17.8 GHz without changing its chirality. Our findings explore a novel way to realize broadband absorption and simultaneously provide a new strategy to design chirality-dependent multi-functional meta-devices. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement