Simple trilayer metamaterial absorber associated with Fano-like resonance

A simple trilayer metamaterial absorber suitable for large area fabrication associated with a Fano-like resonance is numerically investigated and presented at infrared frequencies. The finite-element method-based COMSOL Multiphysics is used for numerical simulations and to understand the mechanism of absorption in the system. The absorber consists of photoresist disk arrays on a silicon substrate followed by a consecutive trilayer of gold, ZnS, and gold. The absorption is caused by the simultaneous excitation of the cavity and guided-mode resonances in the structures, whereas the Fano-like resonance arises due to the interference of these two modes. The coupled mode theory is used to describe the Fano-like resonance in the system. The design can easily be implemented for large area fabrications as it separates the structuring and deposition processes and makes them sequential, and avoids expensive and complex lift-off or etching processes. The spectral position of the resonance can be tuned by just controlling the thickness of the trilayer instead of the structural size and shape modification of the micro/nanostructures as is usually done in conventional metamaterial absorbers.