Self-Affine Graphene Metasurfaces for Tunable Broadband Absorption

Metasurfaces (metamaterials of near-vanishing thickness) are of interest for engineering subwavelength structures with complex responses. Typically a graphene metasurface exhibits just one or two resonances and absorbs light in a narrow frequency band, but this study demonstrates tunable broadband absorption due to hierarchical, fractal structuring. Over a very wide band (about 190% of the central frequency), the average absorption exceeds 20%, without any metallic mirror. This approach to broadband absorbers, and plasmonic components more generally, offers substantially improved performance at terahertz and optical frequencies.