Mechanisms and applications of terahertz metamaterial sensing: a review

Abstract

Terahertz (THz) technology has attracted great worldwide interest and novel high-intensity THz sources and plasmonics are two of the most active fields of recent research. Being situated between infrared light and microwave radiation, the absorption of THz rays in molecular and biomolecular systems is dominated by the excitation of intramolecular and intermolecular vibrations. This indicates that THz technology is an effective tool for sensing applications. However, the low sensitivity of free-space THz detection limits the sensing applications, which gives a great opportunity to metamaterials. Metamaterials are periodic artificial electromagnetic media structured with a size scale smaller than the wavelength of external stimuli. They present localized electric field enhancement and large values of quality factor (Q factor) and show high sensitivity to minor environment changes. In the present work, the mechanism of THz metamaterial sensing and dry sample and microfluidic sensing applications based on metamaterials are introduced. Moreover, new directions of THz metamaterial sensing advancement and introduction of two-dimensional materials and nanoparticles for future THz applications are summarized and discussed.

Terahertz Microfluidic Metamaterial Biosensor for Sensitive Detection of Small-Volume Liquid Samples

“…The resonance frequency difference between the two devices is caused by the SU-8 photoresist used to construct the multi-channels. The transmission spectra after water injection demonstrate that the proposed MMCMMB largely decreases the damping effect to the MM resonance caused by the water absorption [1,35].…”

“…etamaterial (MM) devices can be used for label-free sensing of trace samples due to their sensitive response to subtle changes in the dielectric properties of the surrounding medium and strong electric field enhancement at specific locations on the resonator geometry [1], [2]. The vibrational and rotational energy bands of many biological macromolecules are located in the terahertz (THz) frequency range [3], [4].…”

Liquid crystal tunable terahertz lens with spin-selected focusing property

“…Such active spin-selected lens could be used as THz polarization filters or analyzers [34] and may find practical applications in polarization-based THz imaging and wireless communication [35,36]. Since many biomolecules possess THz fingerprints and are sensitive to incident polarization, the lens could be further applied to biomedical detections [37,38].…”

THz Sensing With Anomalous Extraordinary Optical Transmission Hole Arrays

“…Nevertheless, a major limitation is the relatively large wavelength that makes THz waves largely myopic when the amount of substance to detect is very small. Metasurfaces (of which EOT HAs are a particular example) are revolutionizing sensing all along the electromagnetic spectrum and especially at THz [24][25][26], because they produce a high electric field intensity near the metasurface, enhancing the light-matter interaction with the substance analyzed and producing a sharp change in the spectral response, usually a shift of the metasurface resonance. This allows for a reliable detection even with minute amounts of analyte, a feature that is optimal for label-free thin-film sensing analysis.…”