Ultra-thin broadband nanostructured insulator-metal-insulator-metal plasmonic light absorber.

An ultra-thin nanostructured plasmonic light absorber with an insulator-metal-insulator-metal (IMIM) architecture is designed and numerically studied. The IMIM structure is capable to absorb up to about 82.5% of visible light in a broad wavelength range of 300-750 nm. The absorption by the bottom metal is only 6% of that of the top metal. The results show that the IMIM architecture has weak dependence of the angle of the incident light. Interestingly, by varying the top insulator material the optical absorption spectrum can be shifted more than 180 nm as compared to the conventional air-metal-insulator-metal structure. The IMIM structure can be applied for different plasmonic devices with improved performance.