Ultra-broadband infrared metasurface absorber: comment

In a recently published report, an ultra-broadband gradient-metasurface-based absorber (GMBA) with a single layer of metasurface is proposed by Guo et al. [Opt. Express 24(18), 20586 (2016)1 to realize the ultra-broadband perfect absorption. Moreover, the bandwidth of absorption can be broadened by increasing a layer metasurface on the basis of single-layered GMBA. This comment demonstrates that the cross-polarization reflection is neglected by the authors when they calculate the total absorption in the proposed GMBAs. It is found that there are only two absorption peaks at 8.09 mu m and 9.84 mu m with real absorption rates of 58.4% and 57.1% in a single-layered GMBA. (C) 2018 Optical Society or America under the terms of the OSA Open Access Publishing Agreement