Double-sided polarization-independent plasmonic absorber at near-infrared region.

A double-sided polarization-independent plasmonic absorber is proposed and numerically investigated. Distinct from previously studied absorbers, it could absorb light incident from both sides of the surface through an ultrathin three-layer metal-insulator-metal nanostructure. Patterned metal particles are adopted instead of metal films in this absorber. It shows a high absorbance over a wide incident-angle range at near-infrared region. For electromagnetic waves incident from different sides of the structure, the maximum absorption locates at different wavelengths due to asymmetry. The effective medium theory demonstrates that the whole structure exhibits different impedances for both top and bottom incidences. This double-sided-absorption characteristic could lead to potential applications in thermal emitters, sensing, etc.