Article
Multidisciplinary Sciences
Nicolas Couture, Wei Cui, Markus Lippl, Rachel Ostic, Defi Junior Jubgang Fandio, Eeswar Kumar Yalavarthi, Aswin Vishnuradhan, Angela Gamouras, Nicolas Y. Joly, Jean-Michel Menard
Summary: Slow motion movies can be used to monitor low-energy resonances and reveal fast structural or chemical transitions by replacing images with terahertz waves. By combining THz spectroscopy with a real-time monitoring technique, we have demonstrated the ability to resolve non-reproducible phenomena at 50k frames per second. Our experimental configuration using the photonic time-stretch technique allows for unprecedented data acquisition speeds and enables the study of fast irreversible processes at THz frequencies.
NATURE COMMUNICATIONS
(2023)
Article
Optics
Lei Wang, Kai Kang, Xin Sun, Shibin Wang, Linan Li, Chuanwei Li, Zhiyong Wang
Summary: This paper presents a method to measure the three-dimensional distribution of uniaxial stress based on Terahertz Time Domain Spectroscopy (THz-TDS). The measurement principle was established by combining the computed tomography (CT) method and the photo-elastic effects. A classic filtered back-projection algorithm was used to calculate the three-dimensional stress fields from THz-TDS scanning images. The proposed method was verified by comparing the experiment results with finite element simulation, showing reasonable agreement.
Article
Chemistry, Analytical
Kevin Kolpatzeck, Xuan Liu, Lars Haering, Jan C. Balzer, Andreas Czylwik
Summary: Terahertz time-domain spectroscopy systems driven by monolithic mode-locked laser diodes (MLLDs) offer bandwidths exceeding 1 THz and competitive peak dynamic range. Their ultra-high repetition rates make them suitable for applications where terahertz path length is unknown or fast measurements are needed. The phase accuracy of the system is limited by the synchronization accuracy of subsequent measurements.
Article
Optics
Qinggang Lin, Xinming Yuan, Xuanke Zeng, Yatao Yang, Yi Cai, Xiaowei Lu, Maijie Zheng, Congying Wang, Wenhua Cao, Shixiang Xu
Summary: This paper presents a novel design for single-shot terahertz polarization detection based on terahertz time-domain spectroscopy. Its validity has been confirmed by comparing its detection results with those of the THz common-path spectral interferometer, and the results show that its signal-to-noise ratios are superior to those of the 45 degrees optical bias THz-TDS. The setup works without the need for optical scan and is suitable for applications with poor or no repeatability.
PHOTONICS RESEARCH
(2022)
Article
Chemistry, Analytical
Hungyen Lin, Benjamin P. Russell, Prince Bawuah, J. Axel Zeitler
Summary: This study demonstrates the sensitivity of terahertz technology in measuring water absorption, comparing it to conventional gravimetric analysis to investigate the variation of water content in simple and commercial epoxy systems.
ANALYTICAL CHEMISTRY
(2021)
Article
Optics
Laleh Mohtashemi, Paul Westlund, Derek G. Sahota, Graham B. Lea, Ian Bushfield, Payam Mousavi, J. Steven Dodge
Summary: The presented maximum-likelihood method offers superior parameter estimation in terahertz time-domain spectroscopy and provides a reliable measure of the goodness of fit. Additionally, a simple noise model parameterized by three dominant sources is developed, offering an effective means of estimating materials characteristics.
Article
Materials Science, Characterization & Testing
B. Nidheesh Kumar, M. C. Santhosh Kumar, A. Mercy Latha, Sachinlal Aroliveetil, M. Nallaperumal, Krishnan Balasubramaniam, S. Remakanthan, K. K. Moideenkutty, Shyam S. Nair, L. Mohan Kumar
Summary: This study developed a noncontact, non-invasive method to measure the thickness of polychlorotrifluoroethylene coating on V-type seals using terahertz time-domain spectroscopy. The method achieved close agreement with measurements made using optical microscopy.
NONDESTRUCTIVE TESTING AND EVALUATION
(2023)
Article
Materials Science, Multidisciplinary
Zong Wang, Yanheng Zhang, Ning Lu, Zhiyong Wang, Wei Qiu
Summary: In this study, the stress optical coefficient of the thermal barrier coating (TBC) top coating was measured using reflection-type terahertz time-domain spectroscopy (THz-TDS), and the processed results obtained using the barycenter method were considered as the calibrated stress optical coefficient of TBC due to their sufficient accuracy and stability.
Article
Chemistry, Physical
Srinivasa Rao Konda, Yucai Lin, Rahul A. A. Rajan, Weili Yu, Wei Li
Summary: In this study, terahertz time-domain spectroscopy was performed on organometallic lead bromide and iodide perovskite single crystals. The optical parameters of the crystals were calculated and it was found that they increase with decreasing thickness.
Article
Chemistry, Multidisciplinary
Daniel Molter, Daniel Huebsch, Thorsten Sprenger, Korbinian Hens, Konstantinos Nalpantidis, Frank Platte, Garik Torosyan, Rene Beigang, Joachim Jonuscheit, Georg von Freymann, Frank Ellrich
Summary: Terahertz time-domain spectroscopy is utilized for spectral investigation of materials covered by visibly opaque objects, making it ideal for inspecting mail content. Research on mail inspection in this spectral range includes machine design, optical layouts, data analysis, and implementation.
APPLIED SCIENCES-BASEL
(2021)
Article
Instruments & Instrumentation
Alessia Artesani, Raffaella Lamuraglia, Federica Menegazzo, Stefano Bonetti, Arianna Traviglia
Summary: This work explores the application of terahertz time-domain spectroscopy (THz-TDS) in reflecting configuration on inorganic and mineral pigments. It overcomes the limitations of weak signal intensity, multiple signal losses and distortion, as well as the current scarcity of databases. The experimental procedure and method used to determine the material absorption coefficient of a group of pigments are described in detail, and the vibrational modes of molecular oxides and sulfides are classified for material identification. The results show that this approach is reliable and can be extended to the study of other materials beyond the heritage domain.
APPLIED SPECTROSCOPY
(2023)
Article
Chemistry, Analytical
Jaeseung Im, Taewon Goo, Jugyoung Kim, Soobong Choi, Sung Ju Hong, Young-Mi Bahk
Summary: This study investigated the detection of microplastic embedded in table salts using terahertz time-domain spectroscopy, extracting various optical properties such as refractive index and dielectric constant. The optical properties exhibited volume-ratio-dependence in 0.1-0.5 THz regimes, showing potential for practical applications in detecting microplastic.
Article
Chemistry, Multidisciplinary
Alex M. Potts, Abhay K. Nayak, Michael Nagel, Kelson Kaj, Biljana Stamenic, Demis D. John, Richard D. Averitt, Andrea F. Young
Summary: Free-space time domain THz spectroscopy is suitable for studying electrodynamic responses in condensed matter systems. However, it becomes challenging for samples smaller than the diffraction limit. In this study, we propose an on-chip THz spectrometer with a bandwidth of 200 to 750 GHz. By using this spectrometer, we are able to measure the optical conductivity of a narrow NbN film and observe spectroscopic signatures of the superconducting gap.
Article
Optics
Yi-Fan Zhong, Jiao-Jiao Ren, Li-Juan Li, Ji-Yang Zhang, Dan-Dan Zhang, Jian Gu, Jun-Wen Xue, Qi Chen
Summary: In this study, the stress optical coefficients of a silicone adhesive were measured using terahertz time-domain spectroscopy (THz-TDS), and calculation models for the transmission and reflection stress optical coefficients were derived. The results show that the reflective THz-TDS can be used to measure the stress optical coefficient of the material, compensating for the limitations of the traditional transmission measurement method.
Article
Optics
Kai Kang, Yufeng Du, Shibin Wang, Lin An Li, Zhiyong Wang, Chuanwei Li
Summary: The paper proposes a full-field stress measuring method using terahertz time-domain spectroscopy, based on the stress-optical law. The method is experimentally validated and shows reasonable agreement between experimental results and theoretical solutions.
Article
Physics, Applied
Xiaolong You, Christophe Fumeaux, Withawat Withayachumnankul
Summary: This article provides an overview of the bandwidth limiting factors associated with metasurfaces and introduces a broadband design approach that utilizes network analysis and genetic algorithm for performance optimization.
JOURNAL OF APPLIED PHYSICS
(2022)
Article
Engineering, Electrical & Electronic
Mohamed Shehata, Ke Wang, Julian Webber, Masayuki Fujita, Tadao Nagatsuma, Withawat Withayachumnankul
Summary: The proposed sinc-Lorentzian Nyquist pulse shape outperforms traditional pulse shapes under the influence of timing-jitter in high-speed terahertz communications, improving robustness and performance significantly.
JOURNAL OF LIGHTWAVE TECHNOLOGY
(2022)
Article
Engineering, Electrical & Electronic
Xiaojing Lv, Rajour Tanyi Ako, Madhu Bhaskaran, Sharath Sriram, Christophe Fumeaux, Withawat Withayachumnankul
Summary: This study proposes a terahertz bandpass multilayer FSS filter with adjustable frequency and high power transmission. The filter is insensitive to misalignment and can maintain tunability under different angles of incidence. Compared to existing reconfigurable filters, this design outperforms in terms of tunable range and insertion loss. The design methodology can be applied to other FSS-based structures.
IEEE TRANSACTIONS ON TERAHERTZ SCIENCE AND TECHNOLOGY
(2022)
Article
Engineering, Chemical
D. F. Alves-Lima, X. Li, B. Coulson, E. Nesling, G. A. H. Ludlam, R. Degl'Innocenti, R. Dawson, M. Peruffo, H. Lin
Summary: Perfluorinated sulfonic-acid ionomers are commonly used proton exchange membrane materials, and understanding their structure is crucial for optimizing membrane performance. Terahertz time-domain spectroscopy can analyze water states and retention properties in membranes, and can be applied to thin ionomers. This technique enables rapid parameter space investigation for membrane optimization.
JOURNAL OF MEMBRANE SCIENCE
(2022)
Article
Engineering, Electrical & Electronic
Xiaoran Li, Bryan M. Williams, Robert K. May, Michael J. Evans, Shuncong Zhong, Lynn F. Gladden, Yaochun Shen, J. Axel Zeitler, Hungyen Lin
Summary: This article presents a recurrent neural network approach to optimize waveform selection in inline terahertz pulsed imaging for measuring film coating thickness. The proposed method allows for selecting more waveforms while maintaining excellent agreement with offline thickness measurements. The reduced processing time enables real-time coating monitoring in the pharmaceutical industry, leading to advancements in quality control.
IEEE TRANSACTIONS ON TERAHERTZ SCIENCE AND TECHNOLOGY
(2022)
Article
Plant Sciences
Xinhua Li, Xingyu Yang, Xiaoran Li, Zhiyi Zhao, Zijian Zhang, Hungyen Lin, Dingming Kang, Yaochun Shen
Summary: Seed germination and uniform plant stand are critical for determining final yield. This study used OCT to monitor internal structural changes of pea seeds during germination, finding it to be a fast and nondestructive method for measuring structural indicators in different germination phases.
Article
Electrochemistry
Decio Filipe Alves-Lima, Bryan M. Williams, Harald Schlegl, Gaurav Gupta, Rosa Letizia, Richard Dawson, Hungyen Lin
Summary: This paper explores the feasibility of a compact and low-cost terahertz imaging system for visualizing water build-up inside an operating PEMFC. The results obtained from terahertz imaging are consistent with optical imaging and cell voltage readings, indicating that terahertz imaging can be used as a complementary method for flooding detection in PEMFCs. The proposed setup is also capable of distinguishing the effect of different air flow rates.
Article
Engineering, Electrical & Electronic
Ken Paramayudha, Shengjian Jammy Chen, Withawat Withayachumnankul, Christophe Fumeaux
Summary: This paper introduces a concept of a frequency-reconfigurable circularly polarized antenna with omnidirectional radiation characteristics. The antenna achieves omnidirectional circular polarization through two orthogonal radiators and is empowered with reconfigurability through varactor-loaded slots. The antenna demonstrates a wide CP tuning range and stable omnidirectional patterns.
IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION
(2022)
Article
Polymer Science
Sebastian Engelbrecht, Vincent Pichot, Thomas Goepfert, Hungyen Lin, Bernd M. Fischer
Summary: This study investigated the dynamic behavior of polycarbonate and poly(methyl methacrylate) upon water immersion at different temperatures using gravimetric measurements and terahertz time-domain spectroscopy. The results showed that terahertz measurements provide a reliable non-contact way to study water diffusion in polymers.
Article
Optics
Xiaolong You, Rajour T. T. Ako, Madhu Bhaskaran, Sharath Sriram, Christophe Fumeaux, Withawat Withayachumnankul
Summary: This paper presents a three-layer metasurface-based planar circular polarizer with strong and broadband chirality, overcoming the limitations of conventional non-planar designs and allowing for adjustable functionality and operating bandwidth. Experimental results show that this structure maintains a 15 dB extinction ratio and a transmission efficiency above 92.7% from 251 to 293 GHz. Furthermore, by adjusting the air gap spacings between the metallic layers, it can operate at nearby frequency ranges and is robust to deviations in the air gap spacings.
LASER & PHOTONICS REVIEWS
(2023)
Article
Engineering, Electrical & Electronic
Mingxiang Stephen Li, Ta Van Mai, Christophe Fumeaux, Safumi Suzuki, Withawat Withayachumnankul
Summary: A slot-based RTD structure is proposed to simplify the fabrication process, but it causes an unexpected large tilt angle in the main lobe of its radiation pattern. To solve this issue, a series-fed patch array design is introduced and it directs leakage surface waves to the broadside direction. The simulation and experimental results demonstrate improved radiation performance and potential for future array-level designs and flat lens systems.
IEEE TRANSACTIONS ON TERAHERTZ SCIENCE AND TECHNOLOGY
(2023)
Article
Optics
Mingxiang Stephen Li, Rajour Tanyi Ako, Sharath Sriram, Christophe Fumeaux, Withawat Withayachumnankul
Summary: Uniform illumination is crucial for tera-hertz imaging, and converting a Gaussian beam to a flat top beam is necessary. This study presents a single metasurface lens that efficiently converts a quasi-Gaussian beam to a flat top beam in the near-field region. The design process is divided into three sections to minimize simulation time, and experimental validation confirms high-efficiency conversion at 275 GHz.
Article
Engineering, Electrical & Electronic
Harrison Lees, Cameron Hayes, Withawat Withayachumnankul
Summary: For on-site measurements, compact electronic-based terahertz systems may replace large and expensive conventional terahertz pulse time domain systems. However, the detection of phase in received signals by common electronic detectors complicates the characterization of multilayer samples. In this study, we propose a practical method using swept-source terahertz coherence tomography in reflection configuration for the characterization of in-container liquid samples.
IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS
(2023)
Article
Optics
Daniel Headland, Masayuki Fujita, Guillermo Carpintero, Tadao Nagatsuma, Withawat Withayachumnankul
Summary: The absence of a suitable standard device platform for terahertz waves is hindering the widespread adoption and exploitation of terahertz technology. However, establishing a common platform using substrateless all-silicon microstructures can consolidate design efforts and move beyond disconnected efforts. The all-silicon microstructures offer low loss, compactness, designability, physical rigidity, ease of manufacture, and versatility in integrating various functional devices and systems.
Article
Engineering, Electrical & Electronic
Jan C. Balzer, Clara J. Saraceno, Martin Koch, Priyansha Kaurav, Ullrich R. Pfeiffer, Withawat Withayachumnankul, Thomas Kuerner, Andreas Stoehr, Mohammed El-Absi, Ali Al-Haj Abbas, Thomas Kaiser, Andreas Czylwik
Summary: Terahertz systems offer enormous bandwidths for powerful spectroscopy and high-resolution imaging, as well as potential applications in communication and indoor localization.
IEEE JOURNAL OF MICROWAVES
(2023)
