Dual-band terahertz chiral metasurface absorber with enhanced circular dichroism based on temperature-tunable InSb for sensing applications

Abstract

Circular dichroism (CD) in terahertz (THz) regions has been widely used in biomonitoring, analytical chemistry, communication sensing, and other fields. Herein, we present a simple design for a dual-band THz chiral metasurface absorber (CMA) with a stronger CD effect based on temperature-tunable InSb for enhanced sensing applications. The proposed dual-band CMA consisted of a periodic array of the evolved C-shaped InSb adhered to a copper substrate. The designed CMA at 305 K achieved a right-handed circular polarization (RCP)-selective absorbance of 98.86% and 97.43% at 1.65 THz and 1.89 THz, respectively, and left-handed circular polarization (LCP) absorbance of 9.98% and 22.46%, respectively, and exhibited stronger CD values of 0.89 and 0.75. In addition, the CD properties of the designed CMA can be adjusted by changing the geometrical parameters of the unit-cell structure. The simulated electric field and power follow distributions indicate that this dual-band chiral-selective absorption of the designed CMA is due to the different plasma resonance mode excitations for the incident circular polarization (CP) wave. In addition, the CD properties of the designed CMA can be adjusted by changing the geometrical parameters of the unit-cell structure. Furthermore, CD spectra can be dynamically adjusted by varying the outside temperature and refraction index (RI) of the filled analytes. The designed dual-band CMA can function as a high-performance temperature sensor with sensitivities of 4.68 GHz K⁻¹ and 5.52 GHz K⁻¹ and also as an RI sensor with sensitivities of 1080 GHz RIU⁻¹ and 860 GHz RIU⁻¹, respectively. Our proposed tunable dual-band CMA with its exquisite performance has the potential to be widely applied in diverse areas such as detection, sensing, and other related optoelectronic fields.