High performance broadband absorber in the visible band by engineered dispersion and geometry of a metal-dielectric-metal stack

We propose a nanostructured broadband absorber in the visible regime through designing the dispersion and geometry of a Cu/Si3N4/Cu stack. Two examples with nearly perfect absorption at different spectral ranges are designed based on the special dispersion relationship and fabricated using nanoimprint lithography. Experiments confirm an ultra flat average absorption greater than 80% from 400 nm to 700 nm. The robustness of the design with angle insensitive absorption characteristic is desirable for the applications in thin-film thermal emitters and photovoltaic cells.