Terahertz broadband tunable chiral metamirror based on VO2-metal hybrid structure

Multipath-controlled bidirectional metasurface for multitasking polarization regulation and absorption

In the design of metasurfaces, integrating multiple tasks into a single small unit cell and achieving regulation through various paths pose a serious challenge. In this paper, a multipath-controlled bidirectional metasurface (MCBM) is designed to achieve polarization regulation, perfect absorption and total reflection as multitasking functions. The findings demonstrate that under different excitation conditions, when co-planar polarized terahertz (THz) waves are incident normally on the metasurface, the MCBM can convert co-planar polarization to cross-polarization, co-planar polarization to circular polarization wave in reflection mode, and co-planar polarization to cross-polarization in transmission, respectively. When co-planar polarized THz waves are incident from the back side of the metasurface, the tasks of MCBM change to broadband perfect absorption, total reflection, and transmission co-planar polarization to cross-polarization conversion. Remarkably, all operating frequency bands of these tasks are very approximate. Additionally, the multitasking functions can be switched by altering the excitation conditions, and their performance can be regulated through multipath controls, such as the temperature, voltage, and polarization status. Our design provides an effective strategy for multipath-controlled multitasking integrated devices in the THz band.

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

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.