Compact Dual-Band Terahertz Metamaterial Sensor with High Absorptivity and Angular Stability for Material Characterization

This research investigates the design and performance analysis of a miniaturized, dual-band terahertz (THz) metamaterial sensor engineered for material sensing applications. Operating within the 0.1–1 THz spectral window, the sensor exhibits distinct resonances at 0.5 THz and 0.9 THz, with near-perfect absorptivity levels ranging from 95.5% to 99.9% and 99.4% to 99.9%, respectively. The unit cell incorporates an outer square loop electromagnetically coupled with an inner loop integrated with dual T-shaped stubs, achieving dual resonant modes through mutual inductive and capacitive interactions. The proposed sensor achieves substantial miniaturization, with a footprint of just 0.147 λ₀ × 0.147 λ₀ (λ₀ corresponding to the lowest operating frequency), facilitating dense integration in THz systems. Sensitivity analysis, performed by varying the refractive index of an analyte layer, reveals a resonance shift sensitivity of 0.083 THz/RIU at 0.5 THz and 0.152 THz/RIU at 0.9 THz, indicating strong electromagnetic field confinement and high refractive index contrast sensitivity. The influence of analyte thickness on the spectral response is also evaluated, showing minimal frequency drift, validating the sensor's robustness. The unit cell's symmetric design ensures polarization insensitivity, offering consistent response under both transverse electric (TE) and transverse magnetic (TM) excitations. Furthermore, the sensor demonstrates angular stability up to 60° for oblique incidence, ensuring reliable operation across diverse illumination conditions. The combination of deep subwavelength miniaturization, dual-frequency response, near-unity absorption, and good electromagnetic stability positions the proposed sensor as a highly promising candidate for next-generation THz sensing platforms targeting biochemical, dielectric, and hazardous material analysis.