Characterization of Metamaterials in the Ambient Environment Using Continuous Wave Terahertz Frequency-Domain Spectroscopy

The high sensitivity and selectivity of metamaterial sensors are attractive in many research fields. In this paper, a continuous wave terahertz frequency domain spectrometer is used to characterize the designed SRR structures in a water vapor environment. We show the whole process from simulation design to experimental verification of a metasurface sensor based on a square split-ring resonator. In the frequency range of 0.9-1.4 THz, by adjusting the geometric configuration, we theoretically designed three periodic SRR structures with different resonant frequencies and calculated their S parameters. Then, a sample with a side length of 16 mm was fabricated by lithography, and THz-FDS was used for experimental characterization in an ambient environment without any nitrogen purging. The experimental results are in good agreement with the theoretical analysis, and the resonance frequency offset is less than 0.04 THz. The ultra-high resolution and high SNR of FDS bring robustness to water vapor, which enables the direct use of metamaterials for enhanced sensing and makes the related applications have a more practical prospect.