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https://www.readbyqxmd.com/read/28916819/continuous-beam-steering-through-broadside-using-asymmetrically-modulated-goubau-line-leaky-wave-antennas
#1
Xiao-Lan Tang, Qingfeng Zhang, Sanming Hu, Yaqiang Zhuang, Abhishek Kandwal, Ge Zhang, Yifan Chen
Goubau line is a single-conductor transmission line, featuring easy integration and low-loss transmission properties. Here, we propose a periodic leaky-wave antenna (LWA) based on planar Goubau transmission line on a thin dielectric substrate. The leaky-wave radiations are generated by introducing periodic modulations along the Goubau line. In this way, the surface wave, which is slow-wave mode supported by the Goubau line, achieves an additional momentum and hence enters the fast-wave region for radiations...
September 15, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28914901/interaction-of-surface-plasmon-polaritons-and-acoustic-waves-inside-an-acoustic-cavity
#2
Nikolai Khokhlov, Grigoriy Knyazev, Boris Glavin, Yakov Shtykov, Oleg Romanov, Vladimir Belotelov
In this Letter, we introduce an approach for manipulation of active plasmon polaritons via acoustic waves at sub-terahertz frequency range. The acoustic structures considered are designed as phononic Fabry-Perot microresonators where mirrors are presented with an acoustic superlattice and the structure's surface, and a plasmonic grating is placed on top of the acoustic cavity so formed. It provides phonon localization in the vicinity of the plasmonic grating at frequencies within the phononic stop band enhancing phonon-light interaction...
September 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28914045/electron-transfer-from-bi-isonicotinic-acid-emerges-upon-photodegradation-of-n3-sensitized-tio2-electrodes
#3
Melike Karakus, Wen Zhang, Hans Joachim Räder, Mischa Bonn, Enrique Cánovas
The long-term stability of dye sensitized solar cells (DSSCs) is determined to a large extent by the photodegradation of their sensitizers. Understanding the mechanism of light induced decomposition of dyes sensitizing a mesoporous oxide matrix may therefore contribute to solutions to increase the life span of DSSCs. Here, we investigate, using ultrafast terahertz photoconductivity measurements, the evolution of interfacial electron transfer (ET) dynamics in N3 dye-sensitized mesoporous TiO2 electrodes upon dye photodegradation...
September 15, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28904349/cross-polarization-coupling-terahertz-time-domain-spectroscopy-in-a-semiconductor-based-on-the-hall-effect
#4
Jiangsheng Hu, JinSong Liu, Kejia Wang
We propose a new type of terahertz time-domain spectroscopy in an isotropic semiconductor wafer applied by a magnetic field in which two cross-polarization THz pulses couple with each other via the Hall effect. We built a classic theoretic model to describe cross-polarization coupling THz spectroscopy (CPCTS). Numerical simulations show that the magnetic field can clearly affect the spectral features of the two THz pulses via the Hall effect in which both the magnitude and direction of the magnetic field and the thickness of the wafer play important roles...
September 13, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28901296/negative-terahertz-photoconductivity-in-2d-layered-materials
#5
Junpeng Lu, Hongwei Liu, Jing Sun
The remarkable specialties of 2D layered materials like the wide spectral coverage, high strength and great flexibility endow ultrathin 2D layered materials the potential to meet the criteria of next generation optoelectronic devices. Photoconductivity is one of the critical parameters of materials applied to optoelectronics. Different to the traditional semiconductors, specific ultrathin 2D layers present anomalous negative photoconductivity. This opens a new avenue for designing novel optoelectronic devices...
September 13, 2017: Nanotechnology
https://www.readbyqxmd.com/read/28898820/terahertz-spectroscopic-investigation-of-gallic-acid-and-its-monohydrate
#6
Bo Zhang, Shaoping Li, Chenyang Wang, Tao Zou, Tingting Pan, Jianbing Zhang, Zhou Xu, Guanhua Ren, Hongwei Zhao
The low-frequency spectra of gallic acid (GA) and its monohydrate were investigated by terahertz time-domain spectroscopy (THz-TDS) in the range of 0.5 to 4.5THz. The dehydration process of GA monohydrate was monitored on-line. The kinetic mechanism of the dehydration process was analyzed depending on the THz spectral change at different temperatures. The results indicate that the diffusion of water molecule dominates the speed of the entire dehydration process. Solid-state density functional theory (DFT) calculations of the vibrational modes of both GA and its monohydrate were performed based on their crystalline structures for better interpreting the experimental THz spectra...
September 4, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
https://www.readbyqxmd.com/read/28895970/mechanisms-and-applications-of-terahertz-metamaterial-sensing-a-review
#7
REVIEW
Wendao Xu, Lijuan Xie, Yibin Ying
Terahertz (THz) technology has attracted great worldwide interest and novel high-intensity THz sources and plasmonics are two of the most active fields of recent research. Being situated between infrared light and microwave radiation, the absorption of THz rays in molecular and biomolecular systems is dominated by the excitation of intramolecular and intermolecular vibrations. This indicates that THz technology is an effective tool for sensing applications. However, the low sensitivity of free-space THz detection limits the sensing applications, which gives a great opportunity to metamaterials...
September 12, 2017: Nanoscale
https://www.readbyqxmd.com/read/28892635/ultrafast-silicon-photonics-with-visible-to-mid-infrared-pumping-of-silicon-nanocrystals
#8
Benjamin T Diroll, Katelyn S Schramke, Peijun Guo, Uwe R Kortshagen, Richard D Schaller
Dynamic optical control of infrared (IR) transparency and refractive index is achieved using boron-doped silicon nanocrystals excited with mid-IR optical pulses. Unlike previous silicon-based optical switches, large changes in transmittance are achieved without a fabricated structure by exploiting strong light coupling of the localized surface plasmon resonance (LSPR) produced from free holes of p-type silicon nanocrystals. The choice of optical excitation wavelength allows for selectivity between hole heating and carrier generation through intraband or interband photoexcitation, respectively...
September 18, 2017: Nano Letters
https://www.readbyqxmd.com/read/28891927/differential-cmos-sub-terahertz-detector-with-subthreshold-amplifier
#9
Jong-Ryul Yang, Seong-Tae Han, Donghyun Baek
We propose a differential-type complementary metal-oxide-semiconductor (CMOS) sub-terahertz (THz) detector with a subthreshold preamplifier. The proposed detector improves the voltage responsivity and effective signal-to-noise ratio (SNR) using the subthreshold preamplifier, which is located between the differential detector device and main amplifier. The overall noise of the detector for the THz imaging system is reduced by the preamplifier because it diminishes the noise contribution of the main amplifier...
September 9, 2017: Sensors
https://www.readbyqxmd.com/read/28890744/static-and-time-resolved-terahertz-measurements-of-photoconductivity-in-solution-deposited-ruthenium-dioxide-nanofilms
#10
Brian G Alberding, Paul A DeSario, Christopher R So, Adam D Dunkelberger, Debra R Rolison, Jeffrey C Owrutsky, Edwin J Heilweil
Thin-film ruthenium dioxide (RuO2) is a promising alternative material as a conductive electrode in electronic applications because its rutile crystalline form is metallic and highly conductive. Herein, a solution-deposition multi-layer technique is employed to fabricate ca. 70 ± 20 nm thick films (nanoskins) and terahertz spectroscopy is used to determine their photoconductive properties. Upon calcining at temperatures ranging from 373 K to 773 K, nanoskins undergo a transformation from insulating (localized charge transport) behavior to metallic behavior...
February 23, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
https://www.readbyqxmd.com/read/28890494/characterization-of-inclusions-in-evolution-of-sodium-sulfate-using-terahertz-time-domain-spectroscopy
#11
Rima Bao, Zhikui Wu, Hao Li, Fang Wang, Xinyang Miao, Chengjing Feng
The study of fluid inclusion is one of the important means to understanding the evolution of mineral crystals, and can therefore provide original information of mineral evolution. In the process of evolution, outside factors such as temperature and pressure, directly affect the number and size of inclusions, and thus are related to the properties of crystals. In this paper, terahertz time-domain spectroscopy (THz-TDS) was used to detect sodium sulfate crystals with different growth temperatures, and absorption coefficient spectra of the samples were obtained...
2017: Analytical Sciences: the International Journal of the Japan Society for Analytical Chemistry
https://www.readbyqxmd.com/read/28888977/emerging-technologies-for-the-non-invasive-characterization-of-physical-mechanical-properties-of-tablets
#12
REVIEW
Vivek S Dave, Hend I Shahin, Susanne R Youngren-Ortiz, Mahavir B Chougule, Rahul V Haware
The density, porosity, breaking force, viscoelastic properties, and the presence or absence of any structural defects or irregularities are important physical-mechanical quality attributes of popular solid dosage forms like tablets. The irregularities associated with these attributes may influence the drug product functionality. Thus, an accurate and efficient characterization of these properties is critical for successful development and manufacturing of a robust tablets. These properties are mainly analyzed and monitored with traditional pharmacopeial and non-pharmacopeial methods...
September 6, 2017: International Journal of Pharmaceutics
https://www.readbyqxmd.com/read/28879235/spectral-purity-and-tunability-of-terahertz-quantum-cascade-laser-sources-based-on-intracavity-difference-frequency-generation
#13
Luigi Consolino, Seungyong Jung, Annamaria Campa, Michele De Regis, Shovon Pal, Jae Hyun Kim, Kazuue Fujita, Akio Ito, Masahiro Hitaka, Saverio Bartalini, Paolo De Natale, Mikhail A Belkin, Miriam Serena Vitiello
Terahertz sources based on intracavity difference-frequency generation in mid-infrared quantum cascade lasers (THz DFG-QCLs) have recently emerged as the first monolithic electrically pumped semiconductor sources capable of operating at room temperature across the 1- to 6-THz range. Despite tremendous progress in power output, which now exceeds 1 mW in pulsed and 10 μW in continuous-wave regimes at room temperature, knowledge of the major figure of merits of these devices for high-precision spectroscopy, such as spectral purity and absolute frequency tunability, is still lacking...
September 2017: Science Advances
https://www.readbyqxmd.com/read/28878213/contactless-graphene-conductivity-mapping-on-a-wide-range-of-substrates-with-terahertz-time-domain-reflection-spectroscopy
#14
Hungyen Lin, Philipp Braeuninger-Weimer, Varun S Kamboj, David S Jessop, Riccardo Degl'Innocenti, Harvey E Beere, David A Ritchie, J Axel Zeitler, Stephan Hofmann
We demonstrate how terahertz time-domain spectroscopy (THz-TDS) operating in reflection geometry can be used for quantitative conductivity mapping of large area chemical vapour deposited graphene films on sapphire, silicon dioxide/silicon and germanium. We validate the technique against measurements performed with previously established conventional transmission based THz-TDS and are able to resolve conductivity changes in response to induced back-gate voltages. Compared to the transmission geometry, measurement in reflection mode requires careful alignment and complex analysis, but circumvents the need of a terahertz transparent substrate, potentially enabling fast, contactless, in-line characterisation of graphene films on non-insulating substrates such as germanium...
September 6, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28876957/2d-thz-thz-raman-photon-echo-spectroscopy-of-molecular-vibrations-in-liquid-bromoform
#15
Ian A Finneran, Ralph Welsch, Marco A Allodi, Thomas F Miller, Geoffrey A Blake
Fundamental properties of molecular liquids are governed by long-range interactions that most prominently manifest at terahertz (THz) frequencies. Here we report the detection of nonlinear THz photon-echo (rephasing) signals in liquid bromoform using THz-THz-Raman spectroscopy. Together, the many observed signatures span frequencies from 0.5 to 8.5 THz and result from couplings between thermally populated ladders of vibrational states. The strongest peaks in the spectrum are found to be multiquantum dipole and 1-quantum polarizability transitions and may arise from nonlinearities in the intramolecular dipole moment surface driven by intermolecular interactions...
September 13, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28874955/terahertz-endoscopic-imaging-for-colorectal-cancer-detection-current-status-and-future-perspectives
#16
REVIEW
Pallavi Doradla, Cecil Joseph, Robert H Giles
Terahertz (THz) imaging is progressing as a robust platform for myriad applications in the field of security, health, and material science. The THz regime, which comprises wavelengths spanning from microns to millimeters, is non-ionizing and has very low photon energy: Making it inherently safe for biological imaging. Colorectal cancer is one of the most common causes of death in the world, while the conventional screening and standard of care yet relies exclusively on the physician's experience. Researchers have been working on the development of a flexible THz endoscope, as a potential tool to aid in colorectal cancer screening...
August 16, 2017: World Journal of Gastrointestinal Endoscopy
https://www.readbyqxmd.com/read/28874876/an-ultra-compact-rejection-filter-based-on-spoof-surface-plasmon-polaritons
#17
Shumin Zhao, Hao Chi Zhang, Jiahao Zhao, Wen Xuan Tang
In this paper, we propose a scheme to construct a new type of ultra-compact rejection filter by loading split-ring resonators (SRRs) on the transmission line of spoof surface plasmon polaritons (SPPs). From the dispersion analysis of the spoof SPP transmission line with and without the SRR loading, we clearly reveal the mechanism of the rejection characteristic for this compact filter. Meanwhile, we fabricate two spoof SPPs waveguides loaded with different amounts of metamaterials particles, and experimentally test them using an Agilent Vector Network Analyzer (VNA) and a homemade near-field scanning system...
September 5, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28874725/manipulating-of-different-polarized-reflected-waves-with-graphene-based-plasmonic-metasurfaces-in-terahertz-regime
#18
Li Deng, Yongle Wu, Chen Zhang, Weijun Hong, Biao Peng, Jianfeng Zhu, Shufang Li
A graphene-based plasmonic metasurface which can independently control different polarized electromagnetic waves with reasonably small losses in terahertz regime is proposed and demonstrated in this paper. This metasurface is composed of graphene based elements. Owing to anisotropic plasmonic resonance of the graphene-based elements, the reflected phases and magnitudes of orthogonally polarized waves can be independently controlled by varying dimensions of the element. Four types of graphene-based plasmonic metasurfaces with different reflected phases distributions are synthesized and simulated, exhibiting diverse functions such as polarized beam splitting, beam deflection, and linear-to-circular polarization conversion...
September 5, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28874715/molecular-spectrum-of-laterally-coupled-quantum-rings-under-intense-terahertz-radiation
#19
Henrikh M Baghramyan, Manuk G Barseghyan, David Laroze
We study the influence of intense THz laser radiation and electric field on molecular states of laterally coupled quantum rings. Laser radiation shows the capability to dissociate quantum ring molecule and add 2-fold degeneracy to the molecular states at the fixed value of the overlapping size between rings. It is shown that coupled to decoupled molecular states phase transition points form almost a straight line with a slope equal to two. In addition, the electric field direction dependent energy spectrum shows unexpected oscillations, demonstrating strong coupling between molecular states...
September 5, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28871091/demonstration-of-sub-luminal-propagation-of-single-cycle-terahertz-pulses-for-particle-acceleration
#20
D A Walsh, D S Lake, E W Snedden, M J Cliffe, D M Graham, S P Jamison
The sub-luminal phase velocity of electromagnetic waves in free space is generally unobtainable, being closely linked to forbidden faster than light group velocities. The requirement of sub-luminal phase-velocity in laser-driven particle acceleration schemes imposes a limit on the total acceleration achievable in free space, and necessitates the use of dispersive structures or waveguides for extending the field-particle interaction. We demonstrate a travelling source approach that overcomes the sub-luminal propagation limits...
September 4, 2017: Nature Communications
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