A multiple-band perfect absorber for SEIRA applications

Recently perfect absorbers (PAs) have received significant interest due to their characteristics of complex electric permittivity (epsilon) and magnetic permeability (mu). By rationally designing these artificial structures, the impedance of the perfect absorber can be matched to free space with an independent adjustment in the electric and magnetic resonances, where this structure leads to strong absorption from mid- to near-IR wavelength. In this article, we proposed a multiband PA platform, which simultaneously operates with a near unity absorption at different resonances that could be an ideal candidate for multiple sensing of molecular fingerprints. We numerically analyzed the dependence of the optical response of the PA platform through finite-difference time domain (FDTD) simulations for a fine-tuning mechanism of the PA platform. We theoretically demonstrated the surface enhanced infrared absorption (SEIRA) capability of our PA platform by studying its optical response with a thin protein bilayer and a polymethyl-methacrylate (PMMA) film. As an initial step we experimentally showed the vibrational modes of a thin PMMA film. We believe, our findings could open new avenues for reliable SERIA platforms through providing multiple vibrational finger print information compared to its conventional counterparts relying only on a single sensing data.