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[IEEE 2018 International Symposium on Electromagnetic Compatibility (EMC EUROPE) - Amsterdam (2018.8.27-2018.8.30)] 2018 International Symposium on Electromagnetic Compatibility (EMC EUROPE) - Terahertz Shielding Prediction of Id-Periodic N Anolayered Coatings by an Effective Homogeneous Model
摘要： An innovative effective-medium model of 1D-periodic multilayer coatings is developed by applying the transmission line method. Each period consisting of several layers with subwavelength thickness in the nanometer range is modelled as a homogeneous medium characterized by an effective complex conductivity and unit relative permeability. The resulting effective single layer (ESL), having the same total thickness of the multilayer laminate, is represented by a transfer matrix given by the product of the transmission matrices of the periods composing the structure. The effective homogeneous model is used to compute the shielding effectiveness of 1D-periodic photonic-band-gap transparent coatings made by alternating layers of silver and zinc oxide films in the frequency range up to 10 THz. The good accuracy of the results obtained using the ESL is demonstrated by comparison with the results computed by means of the rigorous multilayer formulation.
关键词： THz shielding effectiveness,1D-periodic multilayer coating,effective homogeneous model
更新于2025-09-23 15:23:52
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[IEEE 2018 International Conference and Exposition on Electrical And Power Engineering (EPE) - Iasi, Romania (2018.10.18-2018.10.19)] 2018 International Conference and Exposition on Electrical And Power Engineering (EPE) - Advanced Image Processing in Support of THz Imaging for Early Detection of Gastric Cancer
摘要： Gastric tumors are still late diagnosed and represent min. 17% of cases leading to metastasis. The ability to visualize the mucosa of the gastrointestinal tract in detail is a requisite for early detection of dysplasia and cancer. Although techniques such as chromoendoscopy, high resolution and magnification endoscopy, narrow band imaging, auto-fluorescence imaging improve the visualization and detection of mucosal lesions, biopsy of the targeted lesion must still be performed for a formal histological diagnosis of cellular and architectural atypical.
关键词： gastric cancer,image processing,THz imaging
更新于2025-09-23 15:22:29
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A polarization-resolved study of nanopatterned photoconductive antenna for enhanced Terahertz emission
摘要： Terahertz (THz) frequencies, despite having the potential for several important applications, have been relatively under-explored in the past owing to the unavailability of proper sources and detectors. The scenario has been changing over the last few decades due to the advent of convenient THz sources and detectors. THz photo-conductive antennas (PCA), due to their attractive features, such as cost-effectiveness, room temperature operation, is playing a key role in current and future research prospect in the field of THz spectroscopy, both as source and detectors. Complex PCA designs have been proposed and studied to boost the THz emission efficiencies. Elucidating the underlying physics in such devices requires a thorough investigation of a few physical parameters. This requires the integration of several experimental techniques under identical conditions. In this article, we show such a study, including a parametric variation of pump polarization, conducted on a PCA with nanopatterned active region which boosts the emitted THz radiation. Through the set of measurements, we unravel the subtle interplay of the various physical processes responsible for the emission of THz radiation from the device.
关键词： characterization setup,enhanced THz generation,Photo-conductive antenna,nano-pattern
更新于2025-09-23 15:22:29
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[IEEE 2018 International Conference on Radar (RADAR) - Brisbane, Australia (2018.8.27-2018.8.31)] 2018 International Conference on Radar (RADAR) - Low-THz Wave Snow Attenuation
摘要： This paper assesses the attenuation of Low-THz waves through various intensities of snowfall experimentally at 300 GHz, and is characterized by measuring the ratio of the received power from the target through the snow precipitation and through the same path with no precipitation. Higher attenuation is measured at higher snowfall rate. Snow events are categorized as "dry snow" and "wet snow". The comparison between the measured attenuation through wet and dry snowfall shows larger attenuation is expected through wet snowfall compared to the same snowfall rate of dry snow. This study is fundamentally important to investigate the effect of adverse weather condition on Low-THz waves and to assess their feasibility for outdoor applications.
关键词： snowfall,specific attenuation,Low-THz wave
更新于2025-09-23 15:22:29
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[IEEE 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz 2018) - Nagoya (2018.9.9-2018.9.14)] 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Intense THz Source of Sub-Cycle Pulses with Tunable Elliptical Polarization
摘要： We propose a new THz source based on a large aperture photoconductive antenna for the generation of intense THz waves with tunable elliptical polarization. We designed an interdigitated structure with vertical and horizontal electrodes to produce half-cycle THz pulses with horizontal and vertical polarizations, respectively. A time delay between the two polarizations is introduced using a quartz window deposited onto the parts of the antenna with horizontal electrodes forming a phase mask. We demonstrate the generation of sub-cycle THz pulses with tunable elliptical polarization and a 70 kV/cm electric field. We show that the polarization state can be varied from linear to quasi-circular.
关键词： elliptical polarization,photoconductive antenna,sub-cycle pulses,THz source,tunable polarization
更新于2025-09-23 15:22:29
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A High-Resolution 220-GHz Ultra-Wideband Fully Integrated ISAR Imaging System
摘要： In this paper, an ultra-wideband fully integrated imaging radar at sub-terahertz (sub-THz) frequencies is presented, which demonstrates a fine lateral resolution without using any focal lens/mirror. We have achieved a lateral resolution of 2 mm for an object at 23-cm distance as well as a range resolution of 2.7 mm. To achieve the decent range resolution, in a frequency modulation continuous wave radar configuration, a state-of-the-art chirp bandwidth (BW) of 62.4 GHz at a center frequency of 221.1 GHz is generated and efficiently radiated. We have presented a design technique for the optimal design of the passive embedding around the core transistor to maximize the tuning BW of the voltage controlled oscillator. At the receiver side, to maximize the intermediate frequency level, a subharmonic mixer is utilized, which is designed for the lowest conversion loss. Finally, to obtain the fine lateral resolution, we have implemented near-field beamforming algorithm based on the inverse synthetic aperture radar (ISAR) systems. The synthesized beamwidth is less than 0.5°; hence, high-resolution images are reconstructed. The system is fabricated in a 55-nm BiCMOS process. To the best of our knowledge, this is the first imaging radar at THz/sub-THz frequencies, which utilizes ISAR to achieve a high lateral resolution while the radar system is fully integrated.
关键词： ultra-wideband,Frequency modulation continuous wave (FMCW),remote sensing,THz,radar,sub-terahertz (sub-THz),oscillator,inverse synthetic aperture radar (ISAR),plane wave
更新于2025-09-23 15:21:21
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Field dependence of THz spectra of effective models for <i>α</i> -RuCl <sub/>3</sub>
摘要： We calculate polarized terahertz (THz) spectra of two effective models for a honeycomb-lattice magnet α-RuCl3 by using a numerical exact-diagonalization method. One of the two models is the ab initio model proposed in H.-S. Kim and H.-Y. Kee [Phys. Rev. B 93, 155143 (2016)] and the other is the large-|K| model that we have proposed by an empirical way in order to explain experimental results for α-RuCl3. We discuss the magnetic-?eld dependence of the lowest-excitation mode in the polarized THz spectra for the two models. We ?nd that the energy gap of the lowest-excitation mode in both models does not close and increases almost linearly above the critical ?eld, where the zigzag order is suppressed. From the obtained results, we point out that the low-energy excitation is mainly governed not by the Kitaev interaction but by the Heisenberg interaction and the off-diagonal interactions.
关键词： exact-diagonalization method,honeycomb-lattice magnet,α-RuCl3,THz spectra,Heisenberg interaction,Kitaev interaction
更新于2025-09-23 15:21:21
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[IEEE 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz2018) - Nagoya, Japan (2018.9.9-2018.9.14)] 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - A Multi-Carrier Signals Generation Based on DPMZM In Parallel for THz Communication system
摘要： In this paper, a multi-carrier THz signals generation scheme is proposed and demonstrated. The scheme is based on DPMZM (dual-parallel Mach-Zehnder modulator) in parallel and recirculating frequency shifter (RFS). By optimizing all the sub-modulators embedded in the RFS, the multi-carrier signals with double frequency interval are generated. A theoretical analysis and simulation experiment is developed, the scheme can generate 20 carriers with 0.1THz frequency interval, and the side-mode suppression ratio (SMSR) is over 25dB.
关键词： side-mode suppression ratio,recirculating frequency shifter,multi-carrier THz signals,DPMZM
更新于2025-09-23 15:21:21
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Durchblick mit Holografie
摘要： Bildgebung mit Terahertzstrahlung basiert bislang auf dem Abscannen eines Objekts mit einem Einzeldetektor. Mikrobolometer-Kameras erm?glichen nun eine Bildgebung wie mit jeder Kameratechnik. Fl?chendetektoren erlauben überdies den Einsatz holografischer Methoden. Trotz der gro?en Wellenl?nge reicht die dreidimensionale Ortsaufl?sung für Anwendungen in der Biomechanik.
关键词： Mikrobolometer-Kamera,Oberfl?chenstruktur,Terahertz-Strahlung,THz-Ptychografie,THz-Holografie,Fingerkuppe,Kontaktfl?che
更新于2025-09-23 15:21:01
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Fabrication of large-scale freestanding THz wire grid polarizers by femtosecond laser micromachining
摘要： High-performance THz polarizers, as a quasi-optical device to manipulate THz waves, are highly demanded for THz spectroscopy and imaging applications. In this work, we have employed the femtosecond laser micro-machining technique to fabricate freestanding THz wire grid polarizers with two kinds of reinforced line structures which weaken the e?ects of gravity sagging and entanglement of long free wires, thus enabling large-scale processing. The e?ect of the reinforced lines on the polarizers were simulated by the Finite-Di?erence Time-Domain (FDTD) method, and the performances of the polarizer were characterized by THz time-domain spectroscopy and compared with that of a commercial wire gird polarizer. The calculated transmittance is in good agreement with the FDTD results. The degree of polarization and the extinction ratio of the polarizer with discontinuous reinforced lines are better than those of a commercial wire grid polarizer.
关键词： Time-domain THz spectroscopy,THz,Femtosecond laser micro-machining,Wire grid polarizer
更新于2025-09-23 15:21:01