Ultra-broadband Near-Unity Light Absorption by Disjunct Scattering Resonances of Disordered Nanounits Created with Atomic Scale Shadowing Effect

Metamaterial perfect absorbers have been the subject of many studies in recent years. Near-unity light harvesting in an ultra-broadband frequency range is the prime goal in many applications such as photoconversion systems. While the most common designs for achieving this goal are periodic plasmonic architectures, this work reveals the unprecedented potential of random designs for ultra-broadband light absorption. A metal-insulator-metal (MIM) structure with a periodically patterned top layer has discrete translational symmetry. The proposed theory, supported by numerical simulations, unveils the fact that breaking this symmetry in the top layer introduces multiple resonant units with separate spectra, and the superposition of these separate resonances broaden the overall response. The random absorber is realized using the oblique angle deposition-induced atomic scale shadowing effect. Based on the experimental results and numerical calculations, the proposed disorder plasmonic design can propose unity absorption (> 90%) over the spectral range from 520 to 1270 nm.