Optically transparent metamirror with broadband chiral absorption in the microwave region

Chiral metamirror is one of the recently developed metadevices which can reflect designated circularly polarized waves, mimicking the exoskeleton of iridescent green beetles. Here, an optically transparent metamirror that can absorb microwave chiral photons in a broadband spectrum is demonstrated. A coupled mode theory is adopted to reveal the underlying physics for the improved bandwidth performance. Excellent agreements have been observed between numerical and experimental results, indicating a bandwidth for chiral absorption as high as 2.37 GHz. The optical transparence of the resistive patterns and substrate make the designed metamirrors suitable as microwave coatings in front of optical devices, which may find potential applications in cascaded optical systems working for both microwave and optical signals.