Broadband infrared plasmonic metamaterial absorber with multipronged absorption mechanisms

A broadband plasmonic metamaterial absorber with near perfect multiband absorption in the infrared region is designed using a metal-insulator-metal configuration and fabricated using photolithography. The metal-insulator-metal configuration consists of a Ti microdisk array, a SiO₂ insulator spacer, and an Al bottom layer. The multiband absorption occurs with near perfect absorption at 4.8-7.5 µm and 9.7-10.5 µm. Ultra-broadband absorption in the mid-IR wavelength range between 3-14 µm is realized by adding a rough photoresist layer on top of the periodic microdisk structures. The multiband absorption is achieved through the combined mechanisms including plasmonic surface lattice resonance, gap plasmon resonance, Fabry-Perot cavity resonance, and the intrinsic phonon-polariton absorption of SiO₂.