Surface-plasmon-induced ultra-broadband light absorber operating in the visible to infrared range

We propose a novel broadband absorber that shows a strong absorption band much broader than that shown in previous work. In our proposed absorber, randomly arranged metal nanobumps are introduced in the incident-side metal layer of a metal / insulator / metal structure. The random structure converts broadband light into surface plasmons without any angular or polarization dependence. Using silver as the metal layer, we obtained an ultrawide region in which the absorption was higher than 50% in the wavelength region from 0.4 to 3.2 mu m, which corresponds to a three-octave bandwidth. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement