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
Engineering, Electrical & Electronic
Jinwoo Lee, Soohyun Kim
Summary: This article introduces an analytical method for measuring the quantitative ratio of components in a mixture using terahertz time-domain spectroscopy (THz-TDS), demonstrating its feasibility in concentration analysis.
IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT
(2021)
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
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
Engineering, Electrical & Electronic
Qi Li, Johanna Kolbel, Terry Threlfall, J. Axel Zeitler
Summary: A versatile setup based on terahertz time-domain spectroscopy has been developed to monitor crystallization process, characterize crystal structures, and investigate solvent dynamics. This setup allows investigation of crystallization processes at different temperatures under static or continuous flow conditions, while an attached optical imaging probe enables real-time monitoring.
IEEE TRANSACTIONS ON TERAHERTZ SCIENCE AND TECHNOLOGY
(2022)
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
Engineering, Electrical & Electronic
Miguel A. Baez-Chorro, Borja Vidal
Summary: This paper develops an iterative algorithm to combine time shifted traces in pulsed terahertz time domain spectroscopy. The algorithm is shown to effectively correct errors due to mechanical sampling and enhance acquisition speed.
IEEE SENSORS JOURNAL
(2022)
Article
Engineering, Electrical & Electronic
Mario Mendez Aller, Duu Sheng Ong, Harrison Lik Nang Lau, Sascha Preu
Summary: This study utilizes broadband terahertz time-domain spectroscopy to determine the biodiesel content in petroleum diesel-biodiesel blends. By modeling the spectra of blend components based on nonpolar characteristics, biodiesel content in diesel can be accurately determined. The method of optimal linear combination of model fits proves to be suitable for real-time applications, and a simpler approach based on maximum observed dispersion can be a distinctive characteristic of a given blend.
IEEE TRANSACTIONS ON TERAHERTZ SCIENCE AND TECHNOLOGY
(2021)
Article
Materials Science, Characterization & Testing
Yi-Fan Zhong, Jiao-Jiao Ren, Li-Juan Li, Ji-Yang Zhang, Dan-Dan Zhang, Jian Gu, Jun-Wen Xue, Qi Chen
Summary: A method for monitoring and evaluating the thickness and damage evolution of bonded interfaces in composite structures under cyclic stress using terahertz technology and SIFT image processing algorithm was proposed, providing valuable insights into the effect of stress load on bonding interface damage evolution.
Article
Engineering, Electrical & Electronic
Uttam Nandi, Moritz Scheer, Hong Lu, Justin C. Norman, Arthur C. Gossard, Sascha Preu
Summary: This article presents the investigation of bias-dependent carrier dynamics in ErAs:In(Al)GaAs superlattice photoconductors and compares the results to a theoretical model. The carrier lifetime decreases with bias for materials without InAlAs layer, and for materials with SL consisting of InGaAs and high-barrier InAlAs layer, the carrier lifetime features a bias-dependent fast decay followed by a bias-independent slower decay. The THz spectra recorded confirm the decrease in carrier lifetime, and the power for high-frequency components shows improvement in agreement with theoretical expectations.
IEEE TRANSACTIONS ON TERAHERTZ SCIENCE AND TECHNOLOGY
(2022)
Review
Engineering, Electrical & Electronic
Andrey Baydin, Takuma Makihara, Nicolas Marquez Peraca, Junichiro Kono
Summary: There are various terahertz-frequency excitations in condensed matter, whose magnetic field dependence offers insight into the states and dynamics of electrons. Studying the frequency, temperature, and magnetic field dependence of the optical conductivity tensor can clarify the microscopic physics behind complex many-body behaviors in solids. Combining advanced terahertz spectroscopy techniques with high magnetic field generation has only been recently realized, leading to the exploration of new fascinating physical phenomena.
FRONTIERS OF OPTOELECTRONICS
(2021)
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
Pharmacology & Pharmacy
Yanhua Bo, Jiyuan Fang, Ziming Zhang, Jiadan Xue, Jianjun Liu, Zhi Hong, Yong Du
Summary: Pharmaceutical cocrystals offer an alternative strategy for improving the physicochemical properties of drugs by changing inter-molecular interactions. In this study, a cocrystal of isoniazid and protocatechuic acid was prepared to optimize the properties of isoniazid, a main drug for treating tuberculosis. The results showed distinct differences between the cocrystal and parent materials in THz-TDS and Raman spectroscopy analysis, providing insight into the molecular-level characterization of the cocrystal.
Article
Materials Science, Ceramics
Xinxi Zeng, Yuhe Liang, Han Zhang, Xiaoqing Xi, Jianguo Cao, Bo Li, Ji Zhou
Summary: A numerical smoothing method using B-spline algorithm was introduced to denoise the THz responses of rare-earth orthoferrites, showing more stability and effectiveness in noise reduction compared to the traditional Savitzky-Golay smoothing method. This approach may offer a promising way to reduce noise in the intrinsic but weak resonances of these materials.
JOURNAL OF THE AMERICAN CERAMIC SOCIETY
(2021)
Article
Optics
Nicolas Couture, Jakob Schlosser, Akif Ahmed, Mamoun Wahbeh, Garland Best, Angela Gamouras, Jean-Michel Menard
Summary: Terahertz time-domain spectroscopy (THz-TDS) is a powerful technique for characterizing a wide range of materials. However, the standard configuration is complex and expensive, limiting its availability. This article presents a compact and cost-effective THz-TDS system that utilizes affordable ultrafast lasers.
Article
Engineering, Electrical & Electronic
N. Surkamp, A. Gerling, J. O'Gorman, M. Honsberg, S. Schmidtmann, U. Nandi, S. Preu, J. Sacher, C. Brenner, M. R. Hofmann
Summary: The study investigates a slotted Y-branch laser diode that emits two spectral modes at a difference frequency of about 1 THz in the context of photonic based cw-THz measurements. The beating frequency of the emitted laser light can be tuned by changing the applied laser current, allowing for potentially fast measurements. A second spectral window at 850 GHz was also discovered, enabling pointwise scanning of the difference frequency for thickness determination applications, such as HRFZ-Si wafer samples.
ELECTRONICS LETTERS
(2021)
Article
Multidisciplinary Sciences
Deniz Turan, Ping Keng Lu, Nezih T. Yardimci, Zhaoyu Liu, Liang Luo, Joong-Mok Park, Uttam Nandi, Jigang Wang, Sascha Preu, Mona Jarrahi
Summary: Semiconductor surface states typically hinder device performance, but in this case, the authors utilize them to enable wavelength conversion. They demonstrate a compact, passive conversion device using plasmon-coupled surface states, achieving efficient conversion of optical frequencies without relying on nonlinear phenomena.
NATURE COMMUNICATIONS
(2021)
Correction
Multidisciplinary Sciences
Deniz Turan, Ping Keng Lu, Nezih T. Yardimci, Zhaoyu Liu, Liang Luo, Joong-Mok Park, Uttam Nandi, Jigang Wang, Sascha Preu, Mona Jarrahi
NATURE COMMUNICATIONS
(2021)
Article
Engineering, Electrical & Electronic
Uttam Nandi, Moritz Scheer, Hong Lu, Justin C. Norman, Arthur C. Gossard, Sascha Preu
Summary: This article presents the investigation of bias-dependent carrier dynamics in ErAs:In(Al)GaAs superlattice photoconductors and compares the results to a theoretical model. The carrier lifetime decreases with bias for materials without InAlAs layer, and for materials with SL consisting of InGaAs and high-barrier InAlAs layer, the carrier lifetime features a bias-dependent fast decay followed by a bias-independent slower decay. The THz spectra recorded confirm the decrease in carrier lifetime, and the power for high-frequency components shows improvement in agreement with theoretical expectations.
IEEE TRANSACTIONS ON TERAHERTZ SCIENCE AND TECHNOLOGY
(2022)
Article
Engineering, Electrical & Electronic
Benedikt Leander Krause, Amlan Kusum Mukherjee, Sascha Preu
Summary: In this paper, a photonic spectrum analyzer is presented for measuring spectral power, linewidth, and harmonics of signals in the terahertz range. By using a photonically generated local oscillator frequency and a photoconductor, the signal under test can be downconverted and measured. The measurement results demonstrate that this method is suitable for measuring signals transported via a dielectric waveguide and characterizing on-chip sources.
IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS
(2023)
Article
Optics
Amlan Kusum Mukherjee, Sven Wassmann, Konstantin Wenzel, Bjoern Globisch, Robert Kohlhaas, Lars Liebermeister, Sascha Preu
Summary: Material characterisation and imaging applications using terahertz radiation have gained interest due to their potential for industrial applications. This work presents a vector-based implementation of the gradient descent algorithm to fit measured transmission and reflection coefficients of multilayered objects to a scattering parameter-based model. The algorithm extracts thicknesses and refractive indices of the layers with a maximum 2% error margin.
Article
Chemistry, Analytical
Christoph Hoog Antink, Romina Schulz, Maurice Rohr, Konstantin Wenzel, Lars Liebermeister, Robert Kohlhaas, Sascha Preu
Summary: We used a high-sampling rate terahertz homodyne spectroscopy system to estimate thoracic movement during breathing of healthy subjects at different frequencies. The THz system provided amplitude and phase information, and the motion signal was derived from the raw phase data. The electrocardiogram (ECG) signal recorded with a chest strap showed suboptimal performance, while the THz system showed good agreement with the measurement protocol, resulting in a root mean square estimation error of 1.40 BPM for all subjects.
Article
Chemistry, Analytical
Rahul Yadav, Florian Ludwig, Fahd Rushd Faridi, J. Michael Klopf, Hartmut G. Roskos, Sascha Preu, Andreas Penirschke
Summary: This study presents the characterization of a Zero-bias Schottky diode-based THz detector that operates up to 5.56 THz. The detector was tested using a table-top system up to 1.2 THz and a Free-Electron Laser facility at frequencies ranging from 1.9 to 5.56 THz. Two measurement techniques were employed to differentiate between sub-ns-scale and ms-scale responsivity. The results show that the detector has a noise equivalent power (NEP) in the range of 10-17 pW/vHz and a voltage and current responsivity of approximately 500 kV/W and 100 mA/W, respectively, within the frequency range of 0.2 to 1.2 THz.
Article
Engineering, Electrical & Electronic
Amlan Kusum Mukherjee, Sven Wassmann, Sascha Preu
Summary: By using digital postprocessing technique, the noise in terahertz systems can be significantly reduced without adding too much processing time, thus improving the signal-to-noise ratio, expanding the operational bandwidth, and enhancing the data quality.
IEEE TRANSACTIONS ON TERAHERTZ SCIENCE AND TECHNOLOGY
(2023)
Article
Engineering, Electrical & Electronic
Sumer Makhlouf, Oleg Cojocari, Martin Hofmann, Tadao Nagatsuma, Sascha Preu, Nils Weimann, Heinz-Wilhelm Huebers, Andreas Stoehr
Summary: This manuscript reports on the latest achievements in terahertz sources and receivers, providing a comprehensive overview of their working principles and applications in THz systems.
IEEE JOURNAL OF MICROWAVES
(2023)
Article
Computer Science, Information Systems
Benedikt Leander Krause, Anuar De Jesus Fernandez Olvera, Sascha Preu
Summary: This paper presents an ultra-broadband and inexpensive photonic spectrum analyzer for wireless signals, which has a wide frequency coverage from microwave to terahertz range. By down-converting the signal using an optical local oscillator, the system achieves a large tuning range without the need for component interchange. Compared to an electronic spectrum analyzer, our system offers similar performance at a fraction of the cost.
Review
Nanoscience & Nanotechnology
Ping-Keng Lu, Anuar de Jesus Fernandez Olvera, Deniz Turan, Tom Sebastian Seifert, Nezih Tolga Yardimci, Tobias Kampfrath, Sascha Preu, Mona Jarrahi
Summary: Efficient terahertz generation and detection are crucial for high-performance terahertz systems. Photomixing process in photo-absorbing semiconductor material enables the generation of terahertz frequency components, which can be radiated or mixed with incoming terahertz waves in terahertz emitters and detectors. Current methods often use semiconductors with short carrier lifetimes, resulting in limited photoconductive gain and optical responsivity. Exploring alternative techniques without relying on these semiconductors is of great importance.
Article
Computer Science, Information Systems
Anuar De Jesus Fernandez Olvera, Benedikt Leander Krause, Sascha Preu
Summary: A new architecture for millimeter-wave spectrum analyzers was proposed, utilizing ErAs:InGaAs photoconductive mixers driven by an ultra-narrow linewidth continuous-wave photonic local oscillator. The system, which does not require external electronic spectrum analyzers or frequency extenders, is demonstrated to operate in the frequency range of 50 to 90 GHz, with potential for extension beyond 300 GHz.
Article
Computer Science, Information Systems
Anuar de Jesus Fernandez Olivera, Benedikt Leander Krause, Andres Betancur-Perez, Uttam Nandi, Cristina de Dios, Pablo Acedo, Sascha Preu
Summary: This new scheme for terahertz pulse detection utilizes optoelectronic downconversion for frequency selective analysis, allowing for ultra-high-resolution measurements without the need for long scanning ranges or synchronization of two MLLs. It serves as a metrology tool for fundamental resolution and stability limits analysis, as well as for examining components or gas spectroscopy.
