All-aluminum hierarchical plasmonic surfaces in the infrared

All-Aluminum metal-insulator-metal resonator structures withmultiple metal-insulator stacks showing resonances in the mid-infrared(MIR) are fabricated. Ultrathin native Al2O3 is used as the insulator layersenabling simple fabrication of the resonator structures. The structures withtwo oxide layers exhibit two distinct resonances in the MIR. Simulation ofthese structures shows confinement of magnetic field to the thicker bottomoxide at the shorter wavelength resonance and to the thinner top oxide at theother resonance. Simulations of higher order hierarchical structures with 3 and 4 oxide layers show multispectral response with precise control of theoxide thicknesses. The studied structures show great potential for IRapplications that require durability and multispectral characteristics.