Ultraviolet broadband plasmonic absorber with dual visible and near-infrared narrow bands

We propose an ultraviolet broadband plasmonic absorber with dual narrow bands located separately in the visible and near-infrared regions. It employs a three-layer dielectric and metallic film structure based on a ring square nanodisk array. The interaction of surface plasmon resonance with a Fabry–Perot cavity resonance results in perfect absorption. The absorption efficiency is greater than 99.9% at wavelengths of 660 and 919 nm (visible and near-infrared), respectively, under normal incidence. In the ultraviolet region from 240 to 500 nm, absorption efficiency of over 90% can be achieved. The geometric symmetry of the ring square makes the perfect absorber polarization-independent and insensitive to large incident angle. This perfect absorber, which combines broadband and narrowband absorption, can be used as sensors, solar cells, or thermal emitters within one integrated device with further investigations.