Robust Characterization of Terahertz Metasurface Sensor With Ultrahigh Frequency Selectivity and Polarization Sensitivity

By enhancing light-matter interaction, terahertz (THz) metasurface can significantly improve the performance of THz spectroscopic sensing. Despite their theoretical promise, a robust and practical characterization method for THz metasurface remains urgently needed. This article presents a novel characterization approach for THz metasurface that is resilient to environmental water vapor, enabling ultrahigh frequency selectivity and polarization sensitivity. The performance of the proposed method is demonstrated using a series of lithography-fabricated split-ring metasurface, theoretically designed to be evenly separated over the 0.6-1.0 THz range. A continuous wave THz frequency-domain spectroscopy system was employed for experimental characterization. Following sophisticated raw photocurrent data processing, ultrahigh frequency resolution (0.05 GHz) spectral characterization was achieved within the frequency range of 0.05 to 1.4 THz. The measured data exhibit linear correlation with the theoretical simulation results, and deviations of the resonance frequencies are less than 0.02 THz. By presenting the characterization results with and without water vapor exhibited in the THz pathway, we demonstrate the robustness of the proposed method in the ambient environment. Furthermore, we incorporated a sample rotating frame into the THz optical path to achieve polarization-sensitive measurements. As the era of 6G integrated sensing and communication approaches, our research significantly advances the practicality of metasurface enhanced THz sensing.