Ultrathin polarization-insensitive, broadband visible absorber based rectangular metagratings

In this paper, we design and numerically investigate an ultrathin polarization-insensitive, broadband visible absorber based rectangular metagratings. The absorber, consisting of a dielectric grating grown in a metallic substrate with a vertically metallic covering, presents an average absorption of 0.975 for TM polarization and 0.911 for TE polarization at normal incidence in the visible regime, respectively. For the incident angle ranges from 0 degrees to 45 degrees, the high absorption is almost unchanged for both polarizations. Moreover, the physical mechanism of broadband absorption is investigated. The strong absorption effect is derived from the excited SPR and CMR in the uniform nanocavity for TM polarization and TE polarization, respectively. Compared with those metasurface absorbers using a 2D array or 1D complicated structures, our design is efficient for both TM and TE polarizations using a straightforward 1D structure that provides excellent optical performance.