Highly sensitive triple-band terahertz perfect metamaterial absorber for sensing applications in organic substance

Abstract A highly efficient metamaterial absorber is designed for terahertz (THz) sensing and multiband super absorption, utilizing plasmonic and metamaterial properties to achieve nearly perfect absorption across multiple frequencies. The proposed microstructure design (53 μm × 55 μm) is composed on a full ground layer and a multiple concentric squared patterned copper ring resonator integrated on an FR-4 substrate exhibits near-perfect absorption at three distinct frequencies (0.717 THz, 1.368 THz, and 3.535 THz), enhancing evanescent waves responses for highly sensitive sensing applications. The modelling and numerical analysis are performed using Finite Difference Time Domain (FDTD) based software (CST Microwave Studio) with a genetic algorithm (GA) employed to optimize the geometric parameters. The proposed metamaterial absorber demonstrates maximum absorption of 99.99% at 0.717 and 3.535 THz and 99.95% at 1.368 THz. The metasurface exhibits stability across varying refractive indices, achieving peak sensitivities of 133, 175, and 479.5 GHz RIU −1 at respective resonance frequencies. By responding to material-induced resonance frequency shifts, the absorber is explicitly optimized for precise detection of organic substances including biomolecules, virology, tissues, chemicals, and oils making it highly suitable for bioanalysis, industrial quality control, and advanced biomedical diagnostics, and covering a broader application scope than most prior works that typically focus on a single class of materials.