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Zhao-Hui Zhai, Sen-Cheng Zhong, Jun Li, Li-Guo Zhu, Kun Meng, Jiang Li, Qiao Liu, Qi-Xian Peng, Ze-Ren Li, Jian-Heng Zhao
Pulsed terahertz spectroscopy is suitable for spectroscopic diagnostics of ultrafast events. However, the study of irreversible or single shot ultrafast events requires ability to record transient properties at multiple time delays, i.e., time resolved at single shot level, which is not available currently. Here by angular multiplexing use of femtosecond laser pulses, we developed and demonstrated a time resolved, transient terahertz time domain spectroscopy technique, where burst mode THz pulses were generated and then detected in a single shot measurement manner...
September 2016: Review of Scientific Instruments
Dong Woo Park, Young Bin Ji, Jehwan Hwang, Cheul-Ro Lee, Sang Jun Lee, Jun Oh Kim, Sam Kyu Noh, Seung Jae Oh, Sang-Hoon Kim, Tae-In Jeon, Kwang-Un Jeong, Jin Soo Kim
We report improvement of terahertz (THz) wave radiation for Si-based catalyst-free InAs nanowires (NWs) by simple dipping into tap water (DTW). In addition, the possibility of using InAs NWs as a cost-effective method for biomedical applications is discussed by comparison to bulk InAs. The peak-to-peak current signals (PPCSs) of InAs NWs measured from THz time-domain spectroscopy increased with increasing NW height. For example, the PPCS of 10 μm-long InAs NWs was 2.86 times stronger than that of 2.1 μm-long NWs...
October 26, 2016: Scientific Reports
Wei Liu, Changhong Liu, Feng Chen, Jianbo Yang, Lei Zheng
Discrimination of genetically modified organisms is increasingly demanded by legislation and consumers worldwide. The feasibility of a non-destructive discrimination of glyphosate-resistant and conventional soybean seeds and their hybrid descendants was examined by terahertz time-domain spectroscopy system combined with chemometrics. Principal component analysis (PCA), least squares-support vector machines (LS-SVM) and PCA-back propagation neural network (PCA-BPNN) models with the first and second derivative and standard normal variate (SNV) transformation pre-treatments were applied to classify soybean seeds based on genotype...
October 26, 2016: Scientific Reports
Young Bin Ji, Seung Jae Oh, Seok-Gu Kang, Jung Heo, Sang-Hoon Kim, Yuna Choi, Seungri Song, Hye Young Son, Se Hoon Kim, Ji Hyun Lee, Seung Joo Haam, Yong Min Huh, Jong Hee Chang, Chulmin Joo, Jin-Suck Suh
Gross total resection (GTR) of glioma is critical for improving the survival rate of glioma patients. One of the greatest challenges for achieving GTR is the difficulty in discriminating low grade tumor or peritumor regions that have an intact blood brain barrier (BBB) from normal brain tissues and delineating glioma margins during surgery. Here we present a highly sensitive, label-free terahertz reflectometry imaging (TRI) that overcomes current key limitations for intraoperative detection of World Health Organization (WHO) grade II (low grade), and grade III and IV (high grade) gliomas...
October 26, 2016: Scientific Reports
Ricardo Vega Monroy, Guillermo Salazar Cohen
In this work we present a theory, which is able to explain the non-monotonic decreasing behavior (observed in experimental data(1-11)) of the graphene terahertz conductivity with the increase of the field frequency. In this connection, the displacement of the structure of topological states inside the energy band gap, which appears in graphene due to the strong photon-electron coupling, and the narrowing of this gap, as result of electron transitions from bound photon-dressed electron states to extended states outside the energy gap driven by the field frequency, lead to a periodic change of singularities near the edge of the band gap, resulting in subtle quantum oscillations of the dynamical terahertz conductivity...
October 25, 2016: Nano Letters
Pablo Alonso-González, Alexey Y Nikitin, Yuanda Gao, Achim Woessner, Mark B Lundeberg, Alessandro Principi, Nicolò Forcellini, Wenjing Yan, Saül Vélez, Andreas J Huber, Kenji Watanabe, Takashi Taniguchi, Félix Casanova, Luis E Hueso, Marco Polini, James Hone, Frank H L Koppens, Rainer Hillenbrand
Terahertz (THz) fields are widely used for sensing, communication and quality control. In future applications, they could be efficiently confined, enhanced and manipulated well below the classical diffraction limit through the excitation of graphene plasmons (GPs). These possibilities emerge from the strongly reduced GP wavelength, λp, compared with the photon wavelength, λ0, which can be controlled by modulating the carrier density of graphene via electrical gating. Recently, GPs in a graphene/insulator/metal configuration have been predicted to exhibit a linear dispersion (thus called acoustic plasmons) and a further reduced wavelength, implying an improved field confinement, analogous to plasmons in two-dimensional electron gases (2DEGs) near conductive substrates...
October 24, 2016: Nature Nanotechnology
Michael Thomas Ruggiero, J Axel Zeitler
Anharmonicity has been shown to be an important piece of the fundamental framework that dictates numerous observable phenomena. In particular, anharmonicity is the driving force of vibrational relaxation processes, mechanisms that are integral to the proper function of numerous chemical processes. However, elucidating its origins has proven difficult due to experimental and theoretical challenges, specifically related to separating the anharmonic contributions from other unrelated effects. While no one technique is particularly suited for providing a complete picture of anharmonicity, by combining multiple complementary methods such a characterisation can be made...
October 21, 2016: Journal of Physical Chemistry. B
Brian G Alberding, Adam J Biacchi, Angela R Hight Walker, Edwin J Heilweil
Tin(II) monosulfide (SnS) is a semiconductor material with an intermediate band gap, high absorption coefficient in the visible range, and earth abundant, non-toxic constituent elements. For these reasons, SnS has generated much interest for incorporation into optoelectronic devices, but little is known concerning the charge carrier dynamics, especially as measured by optical techniques. Here, as opposed to prior studies of vapor deposited films, phase-pure colloidal SnS was synthesized by solution chemistry in three size regimes, ranging from nanometer- to micron-scale (SnS small nanoparticles, SnS medium 2D nanosheets, and SnS large 2D μm-sheets), and evaluated by time-resolved terahertz spectroscopy (TRTS); an optical, non-contact probe of the photoconductivity...
July 21, 2016: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
M Garg, M Zhan, T T Luu, H Lakhotia, T Klostermann, A Guggenmos, E Goulielmakis
The frequency of electric currents associated with charge carriers moving in the electronic bands of solids determines the speed limit of electronics and thereby that of information and signal processing. The use of light fields to drive electrons promises access to vastly higher frequencies than conventionally used, as electric currents can be induced and manipulated on timescales faster than that of the quantum dephasing of charge carriers in solids. This forms the basis of terahertz (10(12) hertz) electronics in artificial superlattices, and has enabled light-based switches and sampling of currents extending in frequency up to a few hundred terahertz...
October 19, 2016: Nature
Aram Gragossian, Denis V Seletskiy, Mansoor Sheik-Bahae
The interaction of intense near- and mid-infrared laser pulses with rare gases has produced bursts of radiation with spectral content extending into the extreme ultraviolet and soft x-ray region of electromagnetic spectrum. On the other end of the spectrum, laser-driven gas plasmas has been shown to produce coherent sub-harmonic optical waveforms, covering from terahertz (THz) to mid- and near-infrared frequency spectral band. Both processes can be enhanced via a combination of a driving field and its second harmonic...
October 19, 2016: Scientific Reports
Benjamin T Diroll, Peijun Guo, Robert P H Chang, Richard D Schaller
Epsilon-near-zero materials may be synthesized as colloidal nanocrystals which display large magnitude sub-picosecond switching of infrared localized surface plasmon resonances. Such nanocrystals offer a solution-processable, scalable source of tunable metamaterials compatible with arbitrary substrates. Under intraband excitation, these nanocrystals display a red-shift of the plasmon feature arising from the low electron heat capacities and conduction band non-parabolicity of the oxide. Under interband pumping, they show in an ultrafast blueshift of the plasmon resonance due to transient increases in the carrier density...
October 18, 2016: ACS Nano
Bo Wang, Baogang Quan, Jingwen He, Zhenwei Xie, Xinke Wang, Junjie Li, Qiang Kan, Yan Zhang
A wavelength de-multiplexing metasurface hologram composed of subwavelength metallic antennas is designed and demonstrated experimentally in the terahertz (THz) regime. Different character patterns are generated at the separated working frequencies 0.50 THz and 0.63 THz which determine a narrow frequency bandwidth of 130 GHz. The two working frequencies are around the central resonance frequency of the antennas where antennas behave strong wavefront modulation. Each antenna is fully utilized to control the wavefront of the metasurface at different frequencies by an optimization algorithm...
October 18, 2016: Scientific Reports
Quan Xu, Xiaoqiang Su, Chunmei Ouyang, Ningning Xu, Wei Cao, Yuping Zhang, Quan Li, Cong Hu, Jianqiang Gu, Zhen Tian, Abul K Azad, Jiaguang Han, Weili Zhang
Recently reported active metamaterial analogues of electromagnetically induced transparency (EIT) are promising in developing novel optical components, such as active slow light devices. However, most of the previous works have focused on manipulating the EIT resonance strength at a fixed characteristic frequency and, therefore, realized on-to-off switching responses. To further extend the functionalities of the EIT effect, here we present a frequency tunable EIT analogue in the terahertz regime by integrating photoactive silicon into the metamaterial unit cell...
October 1, 2016: Optics Letters
Maria Angela B Faustino, Lorenzo P Lopez, Jessica Pauline Afalla, Joselito Muldera, Nathaniel Hermosa, Arnel A Salvador, Armando S Somintac, Elmer S Estacio
A one-order-of-magnitude terahertz (THz) emission enhancement in the transmission geometry, over a 0.7-THz broadband range, was observed in semi-insulating gallium arsenide (SI-GaAs) integrated with a subwavelength one-dimensional metal line array (1DMLA). THz emission of the 1DMLA samples showed an intensity increase and exhibited a full-width-at-half-maximum broadening relative to the emission of the bare substrate. Improved index matching could not account for the observed phenomenon. A nonlinear dependence of the integrated THz emission intensity on the number of illuminated lines and on the pump power was observed...
October 1, 2016: Optics Letters
Yoshiro Urade, Yosuke Nakata, Toshihiro Nakanishi, Masao Kitano
We demonstrate that a self-complementary checkerboard-like metasurface works as a broadband coherent perfect absorber (CPA) when symmetrically illuminated by two counter-propagating incident waves. A theoretical analysis based on wave interference and the results of numerical simulations of the proposed metasurface are provided. In addition, we experimentally demonstrate the proposed CPA in the terahertz regime by using a time-domain spectroscopy technique. We observe that the metasurface can work as a CPA below its lowest diffraction frequency...
October 1, 2016: Optics Letters
Yi Chen, Yue Ban, Qi-Biao Zhu, Xi Chen
Graphene-assisted resonant transmission and enhanced Goos-Hänchen shift are investigated in a two-prism frustrated total internal reflection configuration. Due to the excitation of surface plasmons induced by graphene in a low terahertz frequency range, there exist the resonant transmission and anomalous Goos-Hänchen shifts in such an optical tunneling configuration. As compared to the case of the quantum well, a graphene sheet with unique optical properties can enhance the resonant transmission with a relatively low loss and modulate the large negative and positive Goos-Hänchen shifts by adjusting the chemical potential or electron relaxation time...
October 1, 2016: Optics Letters
Masahiro Sato, Shintaro Takayoshi, Takashi Oka
We propose an ultrafast way to generate spin chirality and spin current in a class of multiferroic magnets using a terahertz circularly polarized laser. Using the Floquet formalism for periodically driven systems, we show that it is possible to dynamically control the Dzyaloshinskii-Moriya interaction in materials with magnetoelectric coupling. This is supported by numerical calculations, by which additional resonant phenomena are found. Specifically, when a static magnetic field is applied in addition to the circularly polarized laser, a large resonant enhancement of spin chirality is observed resembling the electron spin resonance...
September 30, 2016: Physical Review Letters
Z Jin, H B Zhuo, T Nakazawa, J H Shin, S Wakamatsu, N Yugami, T Hosokai, D B Zou, M Y Yu, Z M Sheng, R Kodama
Radially polarized intense terahertz (THz) radiation behind a thin foil irradiated by ultrahigh-contrast ultrashort relativistic laser pulse is recorded by a single-shot THz time-domain spectroscopy system. As the thickness of the target is reduced from 30 to 2 µm, the duration of the THz emission increases from 5 to over 20 ps and the radiation energy increases dramatically, reaching ∼10.5mJ per pulse, corresponding to a laser-to-THz radiation energy conversion efficiency of 1.7%. The efficient THz emission can be attributed to reflection (deceleration and acceleration) of the laser-driven hot electrons by the target-rear sheath electric field...
September 2016: Physical Review. E
I-Tan Lin, Jia-Ming Liu, Hsin-Cheng Tsai, Kaung-Hsiung Wu, Jheng-Yuan Syu, Ching-Yuan Su
The majority of the proposed graphene-based THz devices consist of a metamaterial that can optically interact with graphene. This coupled graphene-metamaterial system gives rise to a family of resonant modes such as the surface plasmon polariton (SPP) modes of graphene, the geometrically induced SPPs, also known as the spoof SPP modes, and the Fabry-Perot (FP) modes. In the literature, these modes are usually considered separately as if each could only exist in one structure. By contrast, in this paper, we show that even in a simple metamaterial structure such as a one-dimensional (1D) metallic slit grating, these modes all exist and can potentially interact with each other...
October 14, 2016: Scientific Reports
Furi Ling, Gang Yao, Jianquan Yao
A plasmon-induced polarization conversion (PIPC) structure based on periodically patterned graphene was demonstrated in the THz regime. By varying the Fermi level of two connected T-shape graphene strips through the electrostatic gating, the peak frequency and the group index in the transparency window can be tuned, which is good agreement with the coupled Lorentz oscillator model. Due to interference between two polarization selective graphene plasmonic resonances coexisting in the planar metamaterial, polarization conversion can be achieved...
October 13, 2016: Scientific Reports
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