Metasurface-Assisted Terahertz Sensing

Abstract

Terahertz (THz) waves, which fall between microwaves and infrared bands, possess intriguing electromagnetic properties of non-ionizing radiation, low photon energy, being highly sensitive to weak resonances, and non-polar material penetrability. Therefore, THz waves are extremely suitable for sensing and detecting chemical, pharmaceutical, and biological molecules. However, the relatively long wavelength of THz waves (30~3000 μm) compared to the size of analytes (1~100 nm for biomolecules, <10 μm for microorganisms) constrains the development of THz-based sensors. To circumvent this problem, metasurface technology, by engineering subwavelength periodic resonators, has gained a great deal of attention to enhance the resonance response of THz waves. Those metasurface-based THz sensors exhibit high sensitivity for label-free sensing, making them appealing for a variety of applications in security, medical applications, and detection. The performance of metasurface-based THz sensors is controlled by geometric structure and material parameters. The operating mechanism is divided into two main categories, passive and active. To have a profound understanding of these metasurface-assisted THz sensing technologies, we review and categorize those THz sensors, based on their operating mechanisms, including resonators for frequency shift sensing, nanogaps for enhanced field confinement, chirality for handedness detection, and active elements (such as graphene and MEMS) for advanced tunable sensing. This comprehensive review can serve as a guideline for future metasurfaces design to assist THz sensing and detection.

Literature Review on Recent Advances on Terahertz Antenna Design

“…Metasurfaces play a crucial role in enhancing THz sensor performance by engineering subwavelength resonators. High-temperature superconducting Josephson plasma emitters enable non-destructive imaging of various objects with high contrast differentiation, making them suitable for security, medical, and material evaluation applications [53]. THz imaging, coupled with image processing algorithms, simplifies non-destructive evaluation processes for fault detection in aircraft composites, including air cavities, debonding, and mechanical damage.…”

Refractive index sensor based on fano-magnetic toroidal quadrupole resonance enabled by bound state in the continuum in all-dielectric metasurface

“…The majority of biomolecules exhibit less energy and non-ionizing properties in this frequency range compared to the X-ray spectrum, primarily due to their rotational and vibrational transitions. Consequently, terahertz waves are well-suited for measuring biomolecular samples with high sensitivity (S) and ease of operation 2 , 6 , 15 . Utilizing intrinsic dielectric materials with low losses and thermal conductivities in the terahertz region instead of metals, with strong confined electromagnetic field, provides a high quality factor (QF) which enhances the sensor parameters such as S and figure of merit (FOM) 1 , 2 , 16 – 20 .…”

Terahertz Metamaterials for Biosensing Applications: A Review

“…THz metamaterial technology, which manifests the advantages of both non-destructive sensing and high sensitivity, is an attractive platform for biosensing applications. There have been several review papers on THz metamaterials for biosensing [45][46][47]; for example, a recent review on THz metamaterial biosensing focused on the structure design of the metamaterials [47]. In this review, we aim to provide a deeper and more comprehensive discussion on THz metamaterial biosensing, including different signals of the THz wave used for detection, various resonances induced in the metamaterials and novel materials used for the metamaterials, to improve the biosensing performance.…”