Omnidirectional broadband absorber for visible light based on a modulated plasmonic multistack grating

We present an ultra-thin film absorber made of a metallic/dielectric (Ni/SiO2) metamaterial with a half cylinder cross section. The proposed structure exhibits high absorption for both polarization modes. The total average absorption is over 96% and 92% for transverse electric (TE) and transverse magnetic (TM) polarization, respectively, for normal incidence in all the visible spectrum. This property is well maintained over a wide range of angles of incidence from 0 degrees to 80 degrees. The effects of the structure periodicity are also investigated for both modes and the results show small changes for variations of the order of 200 nm. We also analyzed the structure for a different number of metal-dielectric pairs considering different layers thicknesses. The results show that the absorber can maintain an excellent absorption even with possible errors during the fabrication process. The proposed structure can be used for a wide range of applications, such as thermal emitters, thermophotovoltaics (TPV), optical energy harvesting, thermal detectors among others where a broadband absorption is required.