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Physics Seminar

Ultra-sensitive THz biosensors based on metasurfaces

Speaker: Prof Teun-Teun Kim, Dr Changwon Seo (University of Ulsan, South Korea)
Date: Friday 4 August 2023
Time: 15:00
Venue: TRH 0.01

In this presentation, I will discuss the latest research findings on terahertz (THz) metamaterials that allow for highly sensitive biomolecule sensing. Specifically, I will cover two sensing methods: direct absorption fingerprint detection achieved by an individual ring-shaped coaxial aperture resonator in combination with near-field spectroscopy, and early detection of Alzheimer\'s disease through an abrupt phase transition near an exceptional point in non-Hermitian metasurfaces. The effectiveness of these sensing techniques has been demonstrated through experimental verification, with the ability to detect minuscule amounts of biomolecules at sub-picomole levels. THz spectroscopy has shown great promise as an analysis technique for investigating the electromagnetic properties of various media in the fields of physics, chemistry, and biology by observing carrier dynamics, molecules,and lattice vibrations [1]. However, due to the extreme size mismatch between hundreds of micrometers long THz waves and sub-100-nanometer-scale biomolecules, weak light-matter interaction has limited the effectiveness of THz waves in biomolecule sensing. Recently, THz plasmonic metamaterials have emerged as a potential solution to this challenge by enhancing the inherently weak light-molecular interaction. Nevertheless, detecting distinctive THz molecular absorption spectroscopy remains technically challenging, as far-field signals collected from a millimeter-wide THz spot tend to be averaged out. Amyloid beta (Aβ) protein is a primary biomarker for early detection of Alzheimer\'s disease (AD). Our previous study revealed that the conductance of Aβ protein gradually decreases as they fibrilize [2]. However, the detection of very low molecular levels below picomole is crucial for early diagnosis of Alzheimer’s disease. In this talk, we will introduce two types of highly sensitive THz metamaterial sensors for spectrallyand spatially selective ultra-sensitive THz fingerprint detection. These sensors integrate a ring-shaped coaxial aperture resonator with a microprobe-based near-field measurement system [3], as well as a non-Hermitian metasurface [4] for detecting a smallamount of Aβ protein. The experimentally verified efficacy of these sensors suggests their potential for sub-picomole level biomolecule sensing. References 1. Ferguson, B. and Zhang, X.-C., Nat. Mat. Vol. 1, 26–33, 2002. 2. Heo, C. et al., ACS Nano, Vol. 14, No. 6, 6548–6558, 2022. 3. Ha, T. et al., Nano Lett., Vol. 22, No. 24, 10200–10207, 2022. 4. Park, S. H. et al., Nano Photon., Vol. 9, No. 5, 1031–1039, 2020. Title: Spectroscopic visualization of photonic dispersion in two-dimensional plasmonic/dielectric lattice structures using Fourier-plane scanning measurement Dr Changwon Seo (Universityof Ulsan) Fourier-plane analysis based on angle resolved reflectance spectroscopy is a technique to measure the momentum space properties of light in a lattice media. By employing a convex lens for optical Fourier transformation, the diffraction pattern induced by the lattice structure can be imaged at the Fourier plane. Furthermore, the photonic dispersion in 2D plasmonic/dielectric lattice structure can be visualized by stacking the spectra, which are obtained from the Fourier plane. Here, we introduce a Fourier-plane analysis method for measuring photonic dispersion in a 2D plasmonic/dielectric lattice structure. Short bio: Teun-Teun Kim is an assistant professor in Department of Semiconductor. He received Ph.D. in physics from the KAIST in 2010. From September 2010 to August 2013, he was a Post-Doctoral Research Fellow at KAIST, and from September 2013 to February 2017, he worked as the Marie Curie Fellow in the Metamaterial Research Centre at University of Birmingham, UK. In March 2017, he was awarded, IBS Young Scientist Fellowship in IBS, CINAP at Sungkyunkwan University. His current research focuses on photonic devices and bio-sensors with metamaterials and plasmonics at THz regime, and 2D materials photonics including graphene and transitionmetal dichalcogenide. Changwon Seo received his PhD from Sungkyunkwan University in 2021. From April 2021 to recent, he was a Post-Doctoral Research Fellow at University of Ulsan. His current research focuses on measuring photnic band structure of 2D photonic lattice structure at visible wavelength range.