Design and analysis of a far-infrared metamaterial perfect absorber with sensing applications

In this paper, we present an analysis and design of a metamaterial as the perfect absorber and refractive index sensor in the far-infrared (IR) region, utilizing the finite element method (FEM). The structure consists of a metal resonator on a silicon dielectric with a bottom copper layer beneath the dielectric. Our results demonstrate that the designed structure achieves nearly perfect absorption of transverse electric (TE) polarization at a resonance wavelength of λ r =9.40µm. This occurs because of the perfect impedance matching condition, which achieves a 99.47% absorption efficiency. This condition is also sensitive to the angle of incidence and causes minimal reflection at the resonating wavelength of λ r . This characteristic makes the designed metamaterial structure suitable for use as a sensor. The structure enables maximum electric field confinement in the gap region (g) of the split ring resonator (SRR) at the metal-dielectric interface. The resonance wavelength can be effectively tuned and optimized by varying the gap size (g), dielectric material, dielectric thickness ( t d ), copper layer thickness ( t c ), and incident angle of the metamaterial absorber (MA). The absorption peak shows a highly sensitive response to changes in the refractive index of the surrounding medium, with a sensitivity of 1600 nm/RIU. This absorber, with its excellent absorption in the far-IR spectrum, holds promising potential for applications in energy harvesting and IR sensing.