Broadband efficient anomalous reflection using an aggressively discretized metasurface.

Aggressive discretization in metasurface design-using the least number of unit cells required-can dramatically decrease the phase coverage requirement, thus allowing the use of simple structure and avoiding unit cells with strong resonance, leading to a simple design with broadband performance. An aggressively discretized metasurface with two unit cells per period can realize efficient anomalous reflection. In this work, we investigate the power efficiency and bandwidth of an aggressively discretized metasurface featuring anomalous reflection. Through spectral domain considerations, we find that the theoretical upper limit for the bandwidth of this metasurface reflecting all the incident power into the desired mode is 67%. With aggressive discretization, we design a metasurface with a simple unit cell structure. By tuning the two unit cells, we achieve a metasurface design that reflects more than 80% of the incidence power into the desired anomalous reflection mode over a broad bandwidth of 53.6%. Such bandwidth is unprecedented for an anomalous reflection metasurface. Finally, we fabricate and experimentally demonstrate our anomalous reflection metasurface and obtain bandwidth and efficiency performances which agree well with simulation.