Optimum design of a novel plasmonic absorber-based material sensor using metaheuristic algorithm
Gayathri Ananthakrishnan, Ruby Dass, Manikandan Narayanan · Physica Scripta · 2025
Abstract This paper presents a miniaturized plasmonic absorber-based material sensor operating at 0.8 THz, designed using a multilayer graphene-polyimide structure. The absorber achieves theoretical near-unity absorptivity (100%) at the resonance frequency and exhibits strong polarization insensitivity and angular stability up to 80° for both polarization modes, attributed to its symmetric and compact geometry of 65 × 65 μm. The electrical size is approximately λ0/5, where λ0 is the free-space wavelength at 0.8 THz, supporting subwavelength operation and enhanced confinement. The structure integrates a cross-slot, cross-dipole, and folded inductive loops to enhance coupling and impedance matching, resulting in a high-Q resonance. A metaheuristic Spider Monkey Algorithm (SMA) is employed to optimize the geometric parameters based on user-defined target frequency specifications, outperforming traditional inbuilt optimizers. The SMA achieves a Root Mean Square Error (RMSE) as low as 0.0131 and a Mean Absolute Percentage Error (MAPE) of 0.105%, indicating high prediction accuracy and model reliability. The optimized structure demonstrates a full width at half maximum (FWHM) of 17 GHz and a quality factor (Q) of approximately 47. The sensor’s refractive index sensitivity is measured at 725 GHz RIU−1, and the figure of merit (FoM) is calculated to be 42.6. These results confirm the sensor’s potential for highly accurate dielectric material characterization in THz sensing applications.