Continuously Frequency-Tuneable Plasmonic Structures for Terahertz Bio-sensing and Spectroscopy

Abstract

Plasmon-based devices are powerful for use in highly sensitive evanescent-field detection and analysis, but they exhibit the problem of limited frequency tunability for fixed structures. This feature causes problems in the multi-frequency investigations required for materials characterization, bio-related research, etc. Here, we propose and fabricate a spiral-shaped plasmonic structure that enables a continuous frequency-tuneable evanescent-field concentration in the terahertz (THz) region with simple operation. The device also increases the electric field intensity at the subwavelength aperture, thus significantly amplifying the transmission. Highly tuneable transmission bands are observed by simply rotating the spiral plasmonic structure, which are in good agreement with the behaviour expected from electromagnetic simulation. Medical examinations are performed by measuring the interactions between the frequency-tuneable plasmons and bio-samples, which enables observing distinct tissue-dependent transmission spectra and images. The developed device simultaneously offers the advantages of both plasmonic devices and frequency-tuneable devices, which can increase the availability and versatility of evanescent-field THz sensing and analysis. The mechanism presented will shed light on THz plasmonics and motivate the implementation of a variety of applications based on plasmon-mediated THz technologies.

Terahertz Sensing Based on Metasurfaces

“…When a sample was coated in one region with d-glucose and fructose, the THz image obtained showed a higher attenuation in the fructose area, as shown in the third column of Figure 4a. [83] (left). Real photograph and normalized THz transmittance image of the nano antenna designed with a drop of fructose (upper-right corner) and d-glucose (lower-left corner) where the transmittance at the fructose area shows a higher attenuation (second-right column).…”

“…These results put into manifest the fact that these antennas, specifically designed for a certain sugar molecule, work [73] for different glucose/sucrose concentrations (second-left column). [83] Copyright 2019, Springer Nature. THz transmittance spectra (bottom-right) for different real market beverages containing different sugar concentrations (top-right).…”

“…[83], a spiral-shaped plasmonic structure working in the THz region was presented, in which, by rotating the spiral structure, highly tunable transmission bands were observed. In ref.…”

Biological characteristics and biomarkers of novel SARS-CoV-2 facilitated rapid development and implementation of diagnostic tools and surveillance measures

“…Another method called Terahertz (THz) is a plasmon-based procedures are great for use as highly sensitive field analysis and detection, but exhibits the challenges of frequency tenability limits designed for fixed structures ( Deng et al, 2019 ). THz-based methods however are showed strong potential to use as a molecular tool for a variety of analytical applications owing to its unique nature, including medicine, security, quality control inspection, and many more ( Cai et al, 2014 ; Clery 2002 ; Kulesa 2011 ; Nakajima et al, 2007 ).…”

Terahertz smart dynamic and active functional electromagnetic metasurfaces and their applications

“…Generally, the interaction between a biological sample and a frequency-tunable plasmon is measured for medical examination, in which case different tissues may require different transmission spectra. In [183], Deng et al proposed a spiral plasma structure consisting of a spiral bulls-eye antenna group and a subwavelength aperture surrounded by concentric grooves. Through this structure, it can be observed that the height of the transmission belt is adjustable, as shown in the illustration on the left panel of figure 9a.…”