Pub Date : 2024-06-21DOI: 10.1109/TTHZ.2024.3417346
Tobias Olaf Buchmann;Yuma Takida;Matej Sebek;Naoya Kawai;Ginji Sugiura;Hiroaki Minamide;Peter Uhd Jepsen;Simon Jappe Lange
Addressing the challenge of achieving high differential sensitivity in terahertz (THz) spectroscopy for spectroscopic analysis, this study evaluates the THz photomultiplier tube (THz-PMT) in conjunction with an injection-seeded THz-wave parametric generator. Through two experimental setups, the performance of THz-PMT is contrasted with a pyro-electric detector, underscoring the benefits of THz-PMT's nonlinear response. The research further delves into the effectiveness of using a THz source and detector independently, offering insights into their potential for advancing THz spectroscopy applications.
{"title":"Leveraging the Nonlinearity of THz Photomultiplier Tubes for Enhanced Spectroscopic Sensitivity","authors":"Tobias Olaf Buchmann;Yuma Takida;Matej Sebek;Naoya Kawai;Ginji Sugiura;Hiroaki Minamide;Peter Uhd Jepsen;Simon Jappe Lange","doi":"10.1109/TTHZ.2024.3417346","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3417346","url":null,"abstract":"Addressing the challenge of achieving high differential sensitivity in terahertz (THz) spectroscopy for spectroscopic analysis, this study evaluates the THz photomultiplier tube (THz-PMT) in conjunction with an injection-seeded THz-wave parametric generator. Through two experimental setups, the performance of THz-PMT is contrasted with a pyro-electric detector, underscoring the benefits of THz-PMT's nonlinear response. The research further delves into the effectiveness of using a THz source and detector independently, offering insights into their potential for advancing THz spectroscopy applications.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 5","pages":"592-598"},"PeriodicalIF":3.9,"publicationDate":"2024-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10568398","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142159800","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-21DOI: 10.1109/TTHZ.2024.3417234
Harrison Lees;Daniel Headland;Withawat Withayachumnankul
All-silicon substrateless waveguides have become a leading contender for terahertz device integration owing to their broad operating bandwidth and exceptional efficiency. However, without metallic confinement, these unshielded waveguides are susceptible to evanescent coupling, requiring that waveguides be placed sparsely to resist unwanted interactions. This sparsity remains a critical obstacle to compact devices and integrated systems. To counter this, we demonstrate substrateless extreme skin-depth waveguides, utilizing a self-supporting anisotropic cladding that markedly reduces the evanescent field penetration into the surrounding cladding, and hence, suppresses cross coupling between waveguides. Here, we achieve 20-dB cross-talk suppression across the WR3.4 band, 220–330 GHz, a 40% fractional bandwidth, with less than 0.5 free-space wavelength separations and coupling lengths exceeding ten free-space wavelengths. In addition, we exploit the low bending loss of this waveguide to realize an efficient and simply designable power divider to realize arbitrary extinction ratios between 1:1 and 10:1. Integrable with existing all-silicon devices, we foresee these techniques enabling the dense integration of terahertz systems with substrateless silicon waveguides.
{"title":"Terahertz Extreme Skin-Depth Waveguides","authors":"Harrison Lees;Daniel Headland;Withawat Withayachumnankul","doi":"10.1109/TTHZ.2024.3417234","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3417234","url":null,"abstract":"All-silicon substrateless waveguides have become a leading contender for terahertz device integration owing to their broad operating bandwidth and exceptional efficiency. However, without metallic confinement, these unshielded waveguides are susceptible to evanescent coupling, requiring that waveguides be placed sparsely to resist unwanted interactions. This sparsity remains a critical obstacle to compact devices and integrated systems. To counter this, we demonstrate substrateless extreme skin-depth waveguides, utilizing a self-supporting anisotropic cladding that markedly reduces the evanescent field penetration into the surrounding cladding, and hence, suppresses cross coupling between waveguides. Here, we achieve 20-dB cross-talk suppression across the WR3.4 band, 220–330 GHz, a 40% fractional bandwidth, with less than 0.5 free-space wavelength separations and coupling lengths exceeding ten free-space wavelengths. In addition, we exploit the low bending loss of this waveguide to realize an efficient and simply designable power divider to realize arbitrary extinction ratios between 1:1 and 10:1. Integrable with existing all-silicon devices, we foresee these techniques enabling the dense integration of terahertz systems with substrateless silicon waveguides.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 5","pages":"758-767"},"PeriodicalIF":3.9,"publicationDate":"2024-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142159953","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-17DOI: 10.1109/TTHZ.2024.3415501
Xiang Lü;Benjamin Röben;Valentino Pistore;Klaus Biermann;Esperanza Luna;Martin Wienold;Heinz-Wilhelm Hübers;Jente R. Wubs;Jean-Pierre H. van Helden;Pierre Gellie;Lutz Schrottke
We report on the development and the application of high-performance terahertz (THz) quantum-cascade lasers (QCLs) based on GaAs/Al $_{x}$ Ga $_{1-x}$ As heterostructures. These lasers with emission frequencies between 2.6 and 4.7 THz are based on a hybrid design, which is preferred for continuous-wave applications. For the design of the active regions, we employ an efficient Fourier-transform-based model, which also allows for the simulation of heterostructures with gradual interfaces. Since the inherent interface width is on the same order as the thickness of the layers in the active region, the use of nominally binary AlAs barriers results in an effective Al content up to $x$$=$ 0.6 for the tallest barriers. For practical applications, Fabry–Pérot lasers based on single-plasmon waveguides are fabricated. Single-mode operation is in most cases achieved by using short cavities. In particular, GaAs/AlAs THz QCLs show a sufficiently high wall plug efficiency so that they can be operated in miniature mechanical cryocoolers. Currently, high-performance THz QCLs are used for commercial continuous-wave, table-top THz systems, local oscillators in 3.5- and 4.7-THz heterodyne spectrometers, and absorption spectrometers for the determination of the density of atomic oxygen in plasmas.
{"title":"Terahertz Quantum-Cascade Lasers: From Design to Applications","authors":"Xiang Lü;Benjamin Röben;Valentino Pistore;Klaus Biermann;Esperanza Luna;Martin Wienold;Heinz-Wilhelm Hübers;Jente R. Wubs;Jean-Pierre H. van Helden;Pierre Gellie;Lutz Schrottke","doi":"10.1109/TTHZ.2024.3415501","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3415501","url":null,"abstract":"We report on the development and the application of high-performance terahertz (THz) quantum-cascade lasers (QCLs) based on GaAs/Al\u0000<inline-formula><tex-math>$_{x}$</tex-math></inline-formula>\u0000Ga\u0000<inline-formula><tex-math>$_{1-x}$</tex-math></inline-formula>\u0000As heterostructures. These lasers with emission frequencies between 2.6 and 4.7 THz are based on a hybrid design, which is preferred for continuous-wave applications. For the design of the active regions, we employ an efficient Fourier-transform-based model, which also allows for the simulation of heterostructures with gradual interfaces. Since the inherent interface width is on the same order as the thickness of the layers in the active region, the use of nominally binary AlAs barriers results in an effective Al content up to \u0000<inline-formula><tex-math>$x$</tex-math></inline-formula>\u0000 \u0000<inline-formula><tex-math>$=$</tex-math></inline-formula>\u0000 0.6 for the tallest barriers. For practical applications, Fabry–Pérot lasers based on single-plasmon waveguides are fabricated. Single-mode operation is in most cases achieved by using short cavities. In particular, GaAs/AlAs THz QCLs show a sufficiently high wall plug efficiency so that they can be operated in miniature mechanical cryocoolers. Currently, high-performance THz QCLs are used for commercial continuous-wave, table-top THz systems, local oscillators in 3.5- and 4.7-THz heterodyne spectrometers, and absorption spectrometers for the determination of the density of atomic oxygen in plasmas.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 5","pages":"579-591"},"PeriodicalIF":3.9,"publicationDate":"2024-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10559383","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142165097","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This article provides a brief overview on THz communications and subsequently focuses on the application of 300 GHz backhaul and fronthaul links. The fundamentals, planning, and software simulation approaches as well as the realized bidirectional 300 GHz demonstrator built within the Horizon 2020 joint EU-Japan project ThoR are described. The ThoR demonstrator uses off-the-shelf modems for network connections and baseband processing, RF front-ends based on InGaAs mHEMT technology and a spurious-free/low-phase noise photonic solution for LO generation. With the ThoR set-up, a net data rate of 2 × 20 Gbps over a distance of 150 m using a total instantaneous bandwidth of 8.64 GHz has been demonstrated. It is also shown that the IEEE Std 802.15.3-2023 protocol works correctly for this application.
{"title":"THz Communications and the Demonstration in the ThoR–Backhaul Link","authors":"Thomas Kürner;Ralf-Peter Braun;Guillaume Ducournau;Uwe Hellrung;Akihiko Hirata;Shintaro Hisatake;Laurenz John;Bo Kum Jung;Ingmar Kallfass;Tetsuya Kawanishi;Keitarou Kondou;Yigal Leiba;Bruce Napier;Ran Timar;Alexandre Renau;Peter Schlegel;Pascal Szriftgiser;Axel Tessmann;Dominik Wrana","doi":"10.1109/TTHZ.2024.3415480","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3415480","url":null,"abstract":"This article provides a brief overview on THz communications and subsequently focuses on the application of 300 GHz backhaul and fronthaul links. The fundamentals, planning, and software simulation approaches as well as the realized bidirectional 300 GHz demonstrator built within the Horizon 2020 joint EU-Japan project ThoR are described. The ThoR demonstrator uses off-the-shelf modems for network connections and baseband processing, RF front-ends based on InGaAs mHEMT technology and a spurious-free/low-phase noise photonic solution for LO generation. With the ThoR set-up, a net data rate of 2 × 20 Gbps over a distance of 150 m using a total instantaneous bandwidth of 8.64 GHz has been demonstrated. It is also shown that the IEEE Std 802.15.3-2023 protocol works correctly for this application.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 5","pages":"554-567"},"PeriodicalIF":3.9,"publicationDate":"2024-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10559434","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142165035","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-11DOI: 10.1109/TTHZ.2024.3412826
Urbi Kundu;Jari Torniainen;Karl Bertling;Mayuri Kashyap;Bogdan C. Donose;Tim Gillespie;Dragan Indjin;Lianhe Li;Edmund H. Linfield;Alexander Giles Davies;Paul Dean;Aparajita Bandyopadhyay;Amartya Sengupta;Aleksandar D. Rakić
This study investigated the use of terahertz (THz) imaging as a rapid, high-fidelity technique for discriminating between genetic variants of the Allium genus based on cellular water dynamics. It has been demonstrated earlier that plant genetic variations can be related to the biochemical and biomechanical alterations of the cell and that in turn affect the water dynamics within the cell. In this article, we show that the water dynamics, when considered in the form of the temporal evolution of the trajectory of the plant's response to THz radiation probe, and measured by a coherent THz transceiver, provides unique signature of the genetic makeup of the plant. Therefore, by exploring these trajectories, we discriminate between closely related variants of the same genus. The technique used for THz probing was the laser feedback interferometry with THz quantum cascade lasers, which enabled fast acquisition of high-resolution THz amplitude and phase images, which were processed into evaporation profiles describing the time-dependent dehydration of the samples. The trajectory of this profile in amplitude–phase reflectivity domain discriminates between different members of the Allium genus. This enables real-time genetic discrimination in agricultural and genome conservation applications.
{"title":"Detecting Genetic Variation in Plants by Mapping Cell Water Dynamics With Terahertz Laser Feedback Interferometry","authors":"Urbi Kundu;Jari Torniainen;Karl Bertling;Mayuri Kashyap;Bogdan C. Donose;Tim Gillespie;Dragan Indjin;Lianhe Li;Edmund H. Linfield;Alexander Giles Davies;Paul Dean;Aparajita Bandyopadhyay;Amartya Sengupta;Aleksandar D. Rakić","doi":"10.1109/TTHZ.2024.3412826","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3412826","url":null,"abstract":"This study investigated the use of terahertz (THz) imaging as a rapid, high-fidelity technique for discriminating between genetic variants of the \u0000<italic>Allium</i>\u0000 genus based on cellular water dynamics. It has been demonstrated earlier that plant genetic variations can be related to the biochemical and biomechanical alterations of the cell and that in turn affect the water dynamics within the cell. In this article, we show that the water dynamics, when considered in the form of the temporal evolution of the trajectory of the plant's response to THz radiation probe, and measured by a coherent THz transceiver, provides unique signature of the genetic makeup of the plant. Therefore, by exploring these trajectories, we discriminate between closely related variants of the same genus. The technique used for THz probing was the laser feedback interferometry with THz quantum cascade lasers, which enabled fast acquisition of high-resolution THz amplitude and phase images, which were processed into evaporation profiles describing the time-dependent dehydration of the samples. The trajectory of this profile in amplitude–phase reflectivity domain discriminates between different members of the \u0000<italic>Allium</i>\u0000 genus. This enables real-time genetic discrimination in agricultural and genome conservation applications.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 5","pages":"665-674"},"PeriodicalIF":3.9,"publicationDate":"2024-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10553260","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142160071","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Terahertz imaging provides valuable insights into the composition and structure of objects or materials, with applications spanning security screening, medical imaging, materials science, and cultural heritage preservation. Despite its widespread utility, traditional terahertz imaging is limited in spatial resolution to approximately 1 mm according to the Abbe's formula. In this article, we propose a novel super-resolution method for terahertz time-domain spectroscopy systems. Our approach involves spatial filtering through scattering in the far-field of high-spatial-frequency components of the imaged sample. This method leverages evanescent wave filtering using a knife edge, akin to a standard structured illumination scheme. We demonstrate improved spatial resolution in slit diffraction, edge imaging, and reflection imaging of structures fabricated on a paper substrate using commonly encountered materials in works of art and documents. Furthermore, we present super-resolved images of an ancient document on parchment, showcasing the effectiveness of our proposed method.
{"title":"Terahertz Imaging Super-Resolution for Documental Heritage Diagnostics","authors":"Danae Antunez Vazquez;Laura Pilozzi;Eugenio DelRe;Claudio Conti;Mauro Missori","doi":"10.1109/TTHZ.2024.3410674","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3410674","url":null,"abstract":"Terahertz imaging provides valuable insights into the composition and structure of objects or materials, with applications spanning security screening, medical imaging, materials science, and cultural heritage preservation. Despite its widespread utility, traditional terahertz imaging is limited in spatial resolution to approximately 1 mm according to the Abbe's formula. In this article, we propose a novel super-resolution method for terahertz time-domain spectroscopy systems. Our approach involves spatial filtering through scattering in the far-field of high-spatial-frequency components of the imaged sample. This method leverages evanescent wave filtering using a knife edge, akin to a standard structured illumination scheme. We demonstrate improved spatial resolution in slit diffraction, edge imaging, and reflection imaging of structures fabricated on a paper substrate using commonly encountered materials in works of art and documents. Furthermore, we present super-resolved images of an ancient document on parchment, showcasing the effectiveness of our proposed method.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 4","pages":"455-465"},"PeriodicalIF":3.9,"publicationDate":"2024-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141495293","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Terahertz (THz) multifrequency digital holography within the range from 1.39–4.25 THz is demonstrated. Holograms are recorded using an optically pumped molecular THz laser operating at emission lines of 1.39-, 2.52-, 3.11-, and 4.25 THz frequencies, and nanometric field effect transistor with integrated patch antennae as a THz detector. It is revealed that phase-shifting methods allow for qualitative reconstruction of multifrequency THz holograms combined into one “colored” image. It provides more information about the low-absorbing objects with additionally improved quality achieved by removing unwanted information related to the so-called dc term and conjugated beam forming a virtual image. It is shown that the THz holography can be applied for the investigation of low-absorbing objects, and it is illustrated via inspection of stacked graphene layers placed on a high-resistivity silicon substrate.
{"title":"Multifrequency Digital Terahertz Holography Within 1.39–4.25 THz Range","authors":"Rusnė Ivaškevičiūtė-Povilauskienė;Ignas Grigelionis;Agnieszka Siemion;Domas Jokubauskis;Kęstutis Ikamas;Alvydas Lisauskas;Linas Minkevičius;Gintaras Valušis","doi":"10.1109/TTHZ.2024.3410670","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3410670","url":null,"abstract":"Terahertz (THz) multifrequency digital holography within the range from 1.39–4.25 THz is demonstrated. Holograms are recorded using an optically pumped molecular THz laser operating at emission lines of 1.39-, 2.52-, 3.11-, and 4.25 THz frequencies, and nanometric field effect transistor with integrated patch antennae as a THz detector. It is revealed that phase-shifting methods allow for qualitative reconstruction of multifrequency THz holograms combined into one “colored” image. It provides more information about the low-absorbing objects with additionally improved quality achieved by removing unwanted information related to the so-called dc term and conjugated beam forming a virtual image. It is shown that the THz holography can be applied for the investigation of low-absorbing objects, and it is illustrated via inspection of stacked graphene layers placed on a high-resistivity silicon substrate.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 5","pages":"568-578"},"PeriodicalIF":3.9,"publicationDate":"2024-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10551534","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142165096","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-06DOI: 10.1109/TTHZ.2024.3410680
Binyi Qin;Jie Qiu;Ruizhao Yang;Yongjin Gan;Hesen Zhong;Qitao Liao;Shaolin Lu;Yun Li
Pharmaceutical cocrystals present a promising avenue for enhancing the physicochemical properties of active pharmaceutical ingredients by modifying intermolecular interactions among raw materials. Theophylline, a methylpurine drug commonly used in respiratory treatments, has limited bioavailability in vivo due to its poor water solubility. In this study, a theophylline–nicotinamide cocrystal was successfully synthesized using the solid-state grinding method. Both the parent materials and the theophylline–nicotinamide cocrystal were characterized using terahertz and Raman spectroscopy. The terahertz spectra exhibited significant differences in the absorption peak between the experimental cocrystal and the parent materials, which were further corroborated by similar findings in the Raman spectra. In addition, density functional theory was employed to optimize the structure of the theophylline–nicotinamide cocrystal and identify its corresponding vibrational modes. Furthermore, intermolecular interactions were analyzed through the independent gradient model based on Hirshfeld partition analysis and Hirshfeld surface analysis. The results demonstrate that the integration of terahertz and Raman spectroscopy with theoretical calculations provides valuable insights into the molecular-level formation of cocrystals. This approach offers crucial information for the analysis of weak interactions in pharmaceutical cocrystals, which is essential for their design and optimization.
{"title":"Structural Investigation of Cocrystal Formed Between Theophylline and Nicotinamide Based on Terahertz and Raman Spectroscopy","authors":"Binyi Qin;Jie Qiu;Ruizhao Yang;Yongjin Gan;Hesen Zhong;Qitao Liao;Shaolin Lu;Yun Li","doi":"10.1109/TTHZ.2024.3410680","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3410680","url":null,"abstract":"Pharmaceutical cocrystals present a promising avenue for enhancing the physicochemical properties of active pharmaceutical ingredients by modifying intermolecular interactions among raw materials. Theophylline, a methylpurine drug commonly used in respiratory treatments, has limited bioavailability in vivo due to its poor water solubility. In this study, a theophylline–nicotinamide cocrystal was successfully synthesized using the solid-state grinding method. Both the parent materials and the theophylline–nicotinamide cocrystal were characterized using terahertz and Raman spectroscopy. The terahertz spectra exhibited significant differences in the absorption peak between the experimental cocrystal and the parent materials, which were further corroborated by similar findings in the Raman spectra. In addition, density functional theory was employed to optimize the structure of the theophylline–nicotinamide cocrystal and identify its corresponding vibrational modes. Furthermore, intermolecular interactions were analyzed through the independent gradient model based on Hirshfeld partition analysis and Hirshfeld surface analysis. The results demonstrate that the integration of terahertz and Raman spectroscopy with theoretical calculations provides valuable insights into the molecular-level formation of cocrystals. This approach offers crucial information for the analysis of weak interactions in pharmaceutical cocrystals, which is essential for their design and optimization.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 4","pages":"476-483"},"PeriodicalIF":3.9,"publicationDate":"2024-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141495191","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-26DOI: 10.1109/TTHZ.2024.3394295
Shinya Nishijima;Yasuaki Monnai
We introduce a topology-optimized metal structure that attains broadband wavefront engineering of guided terahertz waves. While the recent demonstrations of dielectric-free terahertz lenses composed of curved metal surfaces facilitate low-loss and point source-coupled beamforming for the fundamental transverse-electric guided terahertz waves, such designs are significantly constrained in bandwidth due to the frequency dispersion of the mode. To address this challenge, this article employs topology optimization to tailor the effective refractive index profile via the surface structure, achieving broadband manipulation of guided terahertz waves. Experiments around 300 GHz demonstrate the capability to produce a directional beam with an about 15 mm waist from a point source over a 50 GHz bandwidth. Our approach presents a versatile design framework for integrated terahertz systems.
我们介绍了一种拓扑优化的金属结构，它可以实现导波太赫兹波的宽带波前工程。虽然最近展示的由弯曲金属表面组成的无介电太赫兹透镜有助于低损耗和点源耦合的基本横向电导太赫兹波波束成形，但由于模式的频率色散，这种设计在带宽方面受到很大限制。为了应对这一挑战，本文采用拓扑优化技术，通过表面结构定制有效折射率轮廓，实现了对导引太赫兹波的宽带操纵。300 GHz 附近的实验证明，在 50 GHz 的带宽内，能从点源产生腰围约为 15 mm 的定向波束。我们的方法为集成太赫兹系统提供了一个多功能设计框架。
{"title":"Topology-Optimized Metal Structure for Broadband Wavefront Engineering of Guided Terahertz Waves","authors":"Shinya Nishijima;Yasuaki Monnai","doi":"10.1109/TTHZ.2024.3394295","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3394295","url":null,"abstract":"We introduce a topology-optimized metal structure that attains broadband wavefront engineering of guided terahertz waves. While the recent demonstrations of dielectric-free terahertz lenses composed of curved metal surfaces facilitate low-loss and point source-coupled beamforming for the fundamental transverse-electric guided terahertz waves, such designs are significantly constrained in bandwidth due to the frequency dispersion of the mode. To address this challenge, this article employs topology optimization to tailor the effective refractive index profile via the surface structure, achieving broadband manipulation of guided terahertz waves. Experiments around 300 GHz demonstrate the capability to produce a directional beam with an about 15 mm waist from a point source over a 50 GHz bandwidth. Our approach presents a versatile design framework for integrated terahertz systems.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 4","pages":"495-501"},"PeriodicalIF":3.9,"publicationDate":"2024-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141495043","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-25DOI: 10.1109/TTHZ.2024.3393609
Qiyuan Mu;Yuanfeng Zhu;Depeng Kong;Zhengquan He;Hongjun Liu;Lili Wang
This article demonstrates a novel partial negative curvature hollow-core fiber for low-loss terahertz transmission. In the optimized fiber structure, the tubes in the vertical direction are replaced by plate-like dielectric sheets, thereby achieving low loss and low blocked risk of 3D printing, while retaining a small fiber hollow core and fiber diameter. The 3D printed fiber is characterized by a terahertz time-domain spectroscopy system. The obtained transmission spectrum demonstrates the mode beating phenomenon and its peak position varies periodically with fiber length at short distances. The thin antiresonant walls endow the fiber with two broad low-loss windows of 0.2–0.4 THz and 0.55–0.85 THz. Besides, the x -polarization and y -polarization waves achieve minimum losses of 16.2 dB/m@0.28 THz and 16.0 dB/m@0.29 THz, respectively. Furthermore, our fiber has low experimental dispersions, namely −0.18±1.1 ps/THz/cm ( x -pol) and 0.67 ± 0.77 ps/THz/cm ( y -pol). The experimental losses and dispersions match well with the simulation results. Additionally, the simulation results reveal that the fiber has the potential to attain a high birefringence of 10 −3 .
本文展示了一种用于低损耗太赫兹传输的新型部分负曲率中空纤芯光纤。在优化的光纤结构中，垂直方向的管子被板状介质片取代，从而实现了 3D 打印的低损耗和低阻塞风险，同时保留了较小的光纤中空纤芯和光纤直径。太赫兹时域光谱系统对 3D 打印光纤进行了表征。所获得的传输频谱显示了模式跳动现象，其峰值位置在短距离内随光纤长度而周期性变化。薄薄的反谐振壁为光纤提供了 0.2-0.4 太赫兹和 0.55-0.85 太赫兹两个宽阔的低损耗窗口。此外，x 偏振波和 y 偏振波的最小损耗分别为 16.2 dB/m@0.28 THz 和 16.0 dB/m@0.29 THz。此外，我们的光纤具有较低的实验色散，即 -0.18±1.1 ps/THz/cm（x-pol）和 0.67 ± 0.77 ps/THz/cm（y-pol）。实验损耗和色散与模拟结果十分吻合。此外，模拟结果表明，该光纤有可能达到 10-3 的高双折射。
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