Journal articles: 'Terahertz pulses'

1

Petrov, Nikolai I. "Dispersive Propagation of Terahertz Pulses in a Plasmonic Fiber." Fibers 11, no. 7 (July 14, 2023): 62. http://dx.doi.org/10.3390/fib11070062.

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The dispersion properties of surface plasmon polaritons (SPPs) during propagation on metal wires with a dielectric coating in the terahertz frequency range were investigated theoretically. An analytical expression was obtained for a pulsed electric field using the solution of Maxwell equations taking into account high-order dispersion terms. The influence of the dielectric coating on the distortion of the pulse shape was investigated. Unlike uncoated wire, the propagation of surface plasmon pulses along a coated wire is highly dispersive. It was shown that the coating leads to the appearance of a long-chirped signal with a propagation of only a few millimeters, i.e., when a terahertz pulse propagates along a coated wire, it acquires a long oscillatory tail, the frequency of which depends on time.

2

Архипов, Р. М., and Н. Н. Розанов. "Генерация предельно коротких импульсов терагерцового излучения на основе сверхизлучения трехуровневой резонансной среды." Оптика и спектроскопия 129, no. 3 (2021): 319. http://dx.doi.org/10.21883/os.2021.03.50659.274-20.

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The possibility of generating extremely short pulses of terahertz (THz) radiation due to superradiance - collective spontaneous emission of stopped polarization of a thin layer of a three-level resonant medium excited by a pair of attosecond (or femtosecond) pulses is studied theoretically. The source of a terahertz pulse is a pulse of stopped nonlinear polarization of the medium, which occurs in the interval between its excitation and de-excitation. The case of a three-level medium with equidistant energy levels (as in a quantum harmonic oscillator), the transition frequency of which lies in the THz range, is considered. The influence of the populations of the excited levels of the medium on the shape of the terahertz superradiance pulse is discussed.

3

Wynne, Klaas, and Dino A. Jaroszynski. "Superluminal terahertz pulses." Optics Letters 24, no. 1 (January 1, 1999): 25. http://dx.doi.org/10.1364/ol.24.000025.

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Sazonov, S. V., and N. V. Ustinov. "New Soliton Regime of Generation of Broadband Terahertz Radiation by Laser Pulses with Tilted Wave Fronts." JETP Letters 118, no. 6 (September 2023): 408–13. http://dx.doi.org/10.1134/s0021364023602531.

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A new soliton-like regime of generation of terahertz radiation by optical pulses with tilted wave fronts is analyzed. It has been shown that the diffraction of an optical pulse is of fundamental importance for the formation of optical–terahertz soliton. A nonsoliton broadband terahertz component is generated synchronously with the soliton component of radiation. Two matching conditions called “super-Cherenkov” and “anti-Cherenkov” have been revealed under which generation is the most efficient. In the former and latter cases, the optical terahertz soliton propagates ahead and behind the nonsoliton terahertz component, respectively.

5

Seifert, Tom S., Liang Cheng, Zhengxing Wei, Tobias Kampfrath, and Jingbo Qi. "Spintronic sources of ultrashort terahertz electromagnetic pulses." Applied Physics Letters 120, no. 18 (May 2, 2022): 180401. http://dx.doi.org/10.1063/5.0080357.

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Spintronic terahertz emitters are broadband and efficient sources of terahertz radiation, which emerged at the intersection of ultrafast spintronics and terahertz photonics. They are based on efficient spin-current generation, spin-to-charge-current conversion, and current-to-field conversion at terahertz rates. In this Editorial, we review the recent developments and applications, the current understanding of the physical processes, and the future challenges and perspectives of broadband spintronic terahertz emitters.

6

Arkhipov M. V., Arkhipov R. M., and Rosanov N. N. "Generation of unipolar pulses of terahertz radiation with a large electric area." Optics and Spectroscopy 130, no. 8 (2022): 980. http://dx.doi.org/10.21883/eos.2022.08.54771.3703-22.

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A physical situation is proposed and theoretically analyzed, in which, in our opinion, it is possible to generate unipolar terahertz pulses with a large electric area. In this case, the gas in the tube is excited by a femtosecond IR laser pulse. In this case, the tube with gas is placed in a constant external electric field. The generation of a unipolar pulse is based on "three-step scheme" --- ionization of gas atoms by a femtosecond pulse, subsequent acceleration of a free electron in a dc external field and subsequent annihilation of an electron upon collision with a tube wall or another atom (ion). Keywords: unipolar pulses, ultrafast optics, electric pulse area, terahertz radiation, three-step model.

7

Burmistrov E. R. and Avakyants L. P. "Determination of 2DEG parameters in LED heterostructures with three quantum wells In-=SUB=-x-=/SUB=-Ga-=SUB=-1-x-=/SUB=-N/GaN by terahertz time-domain spectroscopy (THz-TDs)." Physics of the Solid State 65, no. 2 (2023): 179. http://dx.doi.org/10.21883/pss.2023.02.55399.503.

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Terahertz time-domain spectroscopy (THz-TDs) has been used to record the resonant frequencies of plasmon oscillations excited in samples of heterostructures with three InxGa1-xN/GaN quantum wells (QWs) by laser pulses with a duration of 130 fs in the temperature range from 90 to 170 K. Fast Fourier transform (FFT) of the time dependence of the electric field of THz-pulses made it possible to obtain the frequency spectra of the power and phase shift of THz-radiation, the interpretation of which made it possible to estimate the pulse relaxation time, mobility and effective mass of two-dimensional electron gas (2DEG) in the heterostructures. Using a series of frequency spectra of the power and phase shift of THz-radiation, the temperature dependences of the effective mass and relaxation time of the 2DEG pulse were obtained. Mobility value 2DEG obtained by the THz-TDs is in good agreement with the data of Hall measurements. Keywords: heterostructures, pulse relaxation time, 2DEG, terahertz radiation, terahertz spectroscopy.

8

Чефонов, О. В., А. В. Овчинников, С. А. Евлашин, and М. Б. Агранат. "Деградация и разрушение тонких стальных пленок при многократном воздействии сверхкоротких импульсов THz-излучения." Письма в журнал технической физики 45, no. 11 (2019): 41. http://dx.doi.org/10.21883/pjtf.2019.11.47824.17775.

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The investigations upon destruction of thin stainless films under the action of ultrashort pulses of directional terahertz radiation are carried out. The terahertz pulse with duration within several picoseconds in fact simulates non-resonance action on matter of quasi-dc electric field with a high electric field strength (up to 20 MV/cm).

9

HANDLEY, J. W., NETTA COHEN, R. D. BOYLE, and ELIZABETH BERRY. "AN EMPIRICAL ANALYSIS OF NOISE IN PULSED TERAHERTZ SYSTEMS." Fluctuation and Noise Letters 06, no. 01 (March 2006): L65—L76. http://dx.doi.org/10.1142/s021947750600315x.

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Terahertz pulsed imaging systems use broadband pulses of sub-millimetre wavelength radiation for spectroscopy and imaging. This Letter demonstrates that a four parameter stable distribution models the observed noise of the pulses, with two of the parameters dependent on material type and thickness. We additionally show that this noise is not characterised by either Gaussian or Gaussian-mixture models.

10

Dem'yanenko M. A. and Startsev V. V. "Application of uncooled microbolometers for detecting pulsed terahertz and infrared radiation." Technical Physics 92, no. 3 (2022): 359. http://dx.doi.org/10.21883/tp.2022.03.53266.190-21.

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Analytical relations for temperature response of the bolometer to periodic radiation pulses are obtained. It is theoretically shown and experimentally confirmed by the example of infrared bolometers that when detecting short radiation pulses, in contrast to the case of constant radiation, increasing the thermal conductivity of the bolometer and, accordingly, decreasing its thermal relaxation time, it is possible to significantly increase the response rate of the receiver, practically without reducing its sensitivity. The possibility of effective registration of pulsed terahertz radiation by microbolometers with a resistively coupled, thermally non-isolated antenna is considered. It is shown that such bolometers, which have increased thermal conductivity and, accordingly, reduced sensitivity to continuous-wave radiation, can be highly effective when detecting pulsed radiation with a duration shorter than the thermal relaxation time of the bolometer. On their basis, uncooled matrix detectors of pulsed terahertz radiation, characterized by a minimum detectable energy of less than 1·10-12 J and a frame rate of up to 1000 Hz, can be developed. Keywords: microbolometer, pulsed terahertz radiation, antenna.

11

Zhang, Zhelin, Jiayang Zhang, Yanping Chen, Tianhao Xia, Linzheng Wang, Bonan Han, Feng He, Zhengming Sheng, and Jie Zhang. "Bessel Terahertz Pulses from Superluminal Laser Plasma Filaments." Ultrafast Science 2022 (March 2, 2022): 1–6. http://dx.doi.org/10.34133/2022/9870325.

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Terahertz radiation with a Bessel beam profile is demonstrated experimentally from a two-color laser filament in air, which is induced by tailored femtosecond laser pulses with an axicon. The temporal and spatial distributions of Bessel rings of the terahertz radiation are retrieved after being collected in the far field. A theoretical model is proposed, which suggests that such Bessel terahertz pulses are produced due to the combined effects of the inhomogeneous superluminal filament structure and the phase change of the two-color laser components inside the plasma channel. These two effects lead to wavefront crossover and constructive/destructive interference of terahertz radiation from different plasma sources along the laser filament, respectively. Compared with other methods, our technique can support the generation of Bessel pulses with broad spectral bandwidth. Such Bessel pulses can propagate to the far field without significant spatial spreading, which shall provide new opportunities for terahertz applications.

12

Avetisyan, Yuri, and Masayoshi Tonouchi. "Nearly Single-Cycle Terahertz Pulse Generation in Aperiodically Poled Lithium Niobate." Photonics 6, no. 1 (January 27, 2019): 9. http://dx.doi.org/10.3390/photonics6010009.

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In the present work, an opportunity of nearly single-cycle THz pulse generation in aperiodically poled lithium niobate (APPLN) crystal is studied. A radiating antenna model is used to simulate the THz generation from chirped APPLN crystal pumped by a sequence of femtosecond laser pulses with chirped delays (m = 1, 2, 3 …) between adjacent pulses. It is shown that by appropriately choosing Δtm, it is possible to obtain temporal overlap of all THz pulses generated from positive (or negative) domains. This results in the formation of a nearly single-cycle THz pulse if the chirp rate of domain length δ in the crystal is sufficiently large. In the opposite case, a few cycle THz pulses are generated with the number of the cycles depending on δ. The closed-form expression for the THz pulse form is obtained. The peak THz electric field strength of 0.3 MV/cm is predicted for APPLN crystal pumped by a sequence of laser pulses with peak intensities of the separate pulse in the sequence of about 20 GW/cm2. By focusing the THz beam and increasing the pump power, the field strength can reach values in the order of few MV/cm.

13

Liu, Xuan, Emmanuelle Jal, Renaud Delaunay, Romain Jarrier, Gheorghe Sorin Chiuzbaian, Grégory Malinowski, Torsten Golz, et al. "Investigating Coherent Magnetization Control with Ultrashort THz Pulses." Applied Sciences 12, no. 3 (January 26, 2022): 1323. http://dx.doi.org/10.3390/app12031323.

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Coherent terahertz control of magnetization dynamics is an area of current interest due to its great potential for the realization of magnetization control on ultrafast timescales in commercial devices. Here we report on an experiment realized at the THz beamline of the free electron laser FLASH at DESY which offers a tunable terahertz radiation source and spontaneously synchronized free-electron laser X-ray pulses to resonantly probe the magnetization state of a ferromagnetic film. In this proof-of-principle experiment, we have excited a thin Permalloy film at different THz wavelengths and recorded the induced magnetization dynamics with photons resonantly tuned to the Ni M2,3 absorption edge. For THz pump pulses including higher orders of the undulator source we observed demagnetization dynamics, which precise shape depended on the employed fundamental wavelength of the undulator source. Analyzing the shape in detail, we can reconstruct the temporal profile of the electric field of the THz pump pulse. This offers a new method for the realization of an in-situ terahertz beamline diagnostic which will help researchers to adjust the pulse characteristics as needed, for example, for future studies of THz induced coherent control of magnetization dynamics.

14

Kang, Taehee, Young-Mi Bahk, and Dai-Sik Kim. "Terahertz quantum plasmonics at nanoscales and angstrom scales." Nanophotonics 9, no. 2 (February 25, 2020): 435–51. http://dx.doi.org/10.1515/nanoph-2019-0436.

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AbstractThrough the manipulation of metallic structures, light–matter interaction can enter into the realm of quantum mechanics. For example, intense terahertz pulses illuminating a metallic nanotip can promote terahertz field–driven electron tunneling to generate enormous electron emission currents in a subpicosecond time scale. By decreasing the dimension of the metallic structures down to the nanoscale and angstrom scale, one can obtain a strong field enhancement of the incoming terahertz field to achieve atomic field strength of the order of V/nm, driving electrons in the metal into tunneling regime by overcoming the potential barrier. Therefore, designing and optimizing the metal structure for high field enhancement are an essential step for studying the quantum phenomena with terahertz light. In this review, we present several types of metallic structures that can enhance the coupling of incoming terahertz pulses with the metals, leading to a strong modification of the potential barriers by the terahertz electric fields. Extreme nonlinear responses are expected, providing opportunities for the terahertz light for the strong light–matter interaction. Starting from a brief review about the terahertz field enhancement on the metallic structures, a few examples including metallic tips, dipole antenna, and metal nanogaps are introduced for boosting the quantum phenomena. The emerging techniques to control the electron tunneling driven by the terahertz pulse have a direct impact on the ultrafast science and on the realization of next-generation quantum devices.

15

Finneran, Ian A., Ralph Welsch, Marco A. Allodi, Thomas F. Miller, and Geoffrey A. Blake. "Coherent two-dimensional terahertz-terahertz-Raman spectroscopy." Proceedings of the National Academy of Sciences 113, no. 25 (June 6, 2016): 6857–61. http://dx.doi.org/10.1073/pnas.1605631113.

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We present 2D terahertz-terahertz-Raman (2D TTR) spectroscopy, the first technique, to our knowledge, to interrogate a liquid with multiple pulses of terahertz (THz) light. This hybrid approach isolates nonlinear signatures in isotropic media, and is sensitive to the coupling and anharmonicity of thermally activated THz modes that play a central role in liquid-phase chemistry. Specifically, by varying the timing between two intense THz pulses, we control the orientational alignment of molecules in a liquid, and nonlinearly excite vibrational coherences. A comparison of experimental and simulated 2D TTR spectra of bromoform (CHBr3), carbon tetrachloride (CCl4), and dibromodichloromethane (CBr2Cl2) shows previously unobserved off-diagonal anharmonic coupling between thermally populated vibrational modes.

16

Zhang, Zhenqing, Fusheng Deng, Feng Wu, and Chengjie Zhu. "Dynamical characteristics of ultrashort terahertz pulse in metamaterials." Laser Physics Letters 19, no. 5 (March 16, 2022): 056001. http://dx.doi.org/10.1088/1612-202x/ac59bc.

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Abstract We develop a time-dependent theoretical approach to study the interaction between the ultrashort terahertz pulse and the metamaterials beyond the steady-state approximation. By using photoconductive silicon, we show that the system dispersion is changed from abnormal to normal via the classical interference effect. As a result, the terahertz pulse propagates through the material with subluminal/superluminal group velocity. We show that it is not accurate to predict the propagation characteristics of the terahertz pulses by using the steady-state solution of coupled wave equations, and the high-order dispersion terms take a significant role which attributes to the pulse shape deformation and the position-dependent group velocity modification. The theoretical approach presented here is essential of describing the propagation properties of the terahertz pulse in metamaterials and is helpful to understand the nature of quantum interference in electromagnetically induced transparency metamaterial.

17

Демьяненко, М. А., and В. В. Старцев. "Применение неохлаждаемых микроболометров для регистрации импульсного терагерцового и инфракрасного излучения." Журнал технической физики 92, no. 3 (2022): 443. http://dx.doi.org/10.21883/jtf.2022.03.52139.190-21.

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Analytical relations for temperature response of the bolometer to periodic radiation pulses are obtained. It is theoretically shown and experimentally confirmed by the example of infrared bolometers that when detecting short radiation pulses, in contrast to the case of constant radiation, increasing the thermal conductivity of the bolometer and, accordingly, decreasing its thermal relaxation time, it is possible to significantly increase the response rate of the receiver, practically without reducing its sensitivity. The possibility of effective registration of pulsed terahertz radiation by microbolometers with a resistively coupled, thermally non-isolated antenna is considered. It is shown that such bolometers, which have increased thermal conductivity and, accordingly, reduced sensitivity to continuous-wave radiation, can be highly effective when detecting pulsed radiation with a duration shorter than the thermal relaxation time of the bolometer. On their basis, uncooled matrix detectors of pulsed terahertz radiation, characterized by a minimum detectable energy of less than 110-12 J and a frame rate of up to 1000 Hz, can be developed.

18

Zhang, Jiangquan, and D. Grischkowsky. "Whispering-gallery mode terahertz pulses." Optics Letters 27, no. 8 (April 15, 2002): 661. http://dx.doi.org/10.1364/ol.27.000661.

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19

Kolner, B. H., R. A. Buckles, P. M. Conklin, and R. P. Scott. "Plasma Characterization With Terahertz Pulses." IEEE Journal of Selected Topics in Quantum Electronics 14, no. 2 (2008): 505–12. http://dx.doi.org/10.1109/jstqe.2007.913395.

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20

Bromage, Jake, Stojan Radic, G. P. Agrawal, Carlos R. Stroud, Jr., P. M. Fauchet, and Roman Sobolewski. "Spatiotemporal Shaping of Terahertz Pulses." Optics and Photonics News 8, no. 12 (December 1, 1997): 47. http://dx.doi.org/10.1364/opn.8.12.000047.

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21

Bromage, Jake, Stojan Radic, G. P. Agrawal, C. R. Stroud, P. M. Fauchet, and Roman Sobolewski. "Spatiotemporal shaping of terahertz pulses." Optics Letters 22, no. 9 (May 1, 1997): 627. http://dx.doi.org/10.1364/ol.22.000627.

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22

Johnson, J. L., T. D. Dorney, and D. M. Mittleman. "Interferometric imaging with terahertz pulses." IEEE Journal of Selected Topics in Quantum Electronics 7, no. 4 (2001): 592–99. http://dx.doi.org/10.1109/2944.974230.

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23

Dorney, Timothy D., William W. Symes, and Daniel M. Mittleman. "Multistatic Reflection Imaging with Terahertz Pulses." International Journal of High Speed Electronics and Systems 13, no. 02 (June 2003): 677–99. http://dx.doi.org/10.1142/s0129156403001855.

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Recent advances in the technique of terahertz time-domain spectroscopy have led to the development of the first fiber-coupled room-temperature broadband terahertz sources and detectors. The fiber coupling permits the repositioning of the emitter and receiver antennas without loss of temporal calibration or alignment, thus enabling multistatic imaging. We describe a new imaging method which exploits this new capability. This technique emulates the data collection and image processing procedures developed for geophysical prospecting. We use a migration procedure to solve the inverse problem; this permits us to reconstruct the location, shape, and refractive index of targets. We show examples for both metallic and dielectric model targets, and we perform velocity analysis on dielectric targets to estimate the refractive indices of imaged components. These results broaden the capabilities of terahertz imaging systems, and also demonstrate the viability of the THz system as a test bed for the exploration of new seismic processing methods.

24

Yang, Peidi, Baolong Zhang, Jinglong Ma, Yutong Li, Jungang Miao, and Xiaojun Wu. "Nonlinear terahertz effects of gold nanofilms." Terahertz Science and Technology 14, no. 1 (March 2021): 20–30. http://dx.doi.org/10.1051/tst/2021141020.

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Nonlinear interaction between strong-field terahertz electromagnetic waves and matters will become one of the next hot research frontiers in nonlinear optics. However, the lack of strong terahertz radiation sources and appropriate nonlinear terahertz materials have impeded its progress. Here we systematically have investigated the strong-field terahertz nonlinear effects of gold (Au) nanofilms on different substrates, including SiO2, high-resistivity Si and SiO2-high-resistivity Si hybrid substrates. The strong-field terahertz waves are emitted from lithium niobate crystals via tilted pulse front technique, and obvious nonlinear transmission responses are observed along with varying the incident field strengths for all the Au samples on the three types of the substrates. The nonlinear behavior is enhanced when the gold nanofilm thickness increases, which can be qualitatively understood by introducing the quantum tunneling effect and carrier multiplication theory generated at the Au nano-slits under the illumination of the strong-field terahertz pulses. Our demonstrations not only open a new paradigm for nonlinear terahertz investigations and future high-speed terahertz devices, but also provide an effective platform for exploring extreme terahertz sciences.

25

Malevich, Vitaly Leonidovich, Pavel Aliaksandravich Ziaziulia, Ričardas Norkus, Vaidas Pačebutas, Ignas Nevinskas, and Arūnas Krotkus. "Terahertz Pulse Emission from Semiconductor Heterostructures Caused by Ballistic Photocurrents." Sensors 21, no. 12 (June 12, 2021): 4067. http://dx.doi.org/10.3390/s21124067.

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Terahertz radiation pulses emitted after exciting semiconductor heterostructures by femtosecond optical pulses were used to determine the electron energy band offsets between different constituent materials. It has been shown that when the photon energy is sufficient enough to excite electrons in the narrower bandgap layer with an energy greater than the conduction band offset, the terahertz pulse changes its polarity. Theoretical analysis performed both analytically and by numerical Monte Carlo simulation has shown that the polarity inversion is caused by the electrons that are excited in the narrow bandgap layer with energies sufficient to surmount the band offset with the wide bandgap substrate. This effect is used to evaluate the energy band offsets in GaInAs/InP and GaInAsBi/InP heterostructures.

26

Bidhendi, Mahdi M., Ivette J. Bermudez Macias, Rosen Ivanov, Mikhail V. Yurkov, and Stefan Düsterer. "FEL Pulse Duration Evolution along Undulators at FLASH." Applied Sciences 12, no. 14 (July 12, 2022): 7048. http://dx.doi.org/10.3390/app12147048.

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Self-amplified spontaneous-emission (SASE) free-electron lasers (FELs) deliver ultrashort pulses with femtosecond durations. Due to the fluctuating nature of the radiation properties of SASE FELs, characterizing FEL pulses on a single-shot basis is necessary. Therefore, we use terahertz streaking to characterize the temporal properties of ultrashort extreme ultraviolet pulses from the free-electron laser in Hamburg (FLASH). In this study, pulse duration as well as pulse energy are measured in a wavelength range from 8 to 34 nm as functions of undulators contributing to the lasing process. The results are compared to one-dimensional and three-dimensional, time-dependent FEL simulations.

27

Jafarzadeh, Hossein, Elnaz Ahmadi Sangachin, and Seyyed Hossein Asadpour. "Controlling of group velocity via terahertz signal radiation in a defect medium doped by four-level InGaN/GaN quantum dot nanostructure." Modern Physics Letters B 29, no. 20 (July 26, 2015): 1550104. http://dx.doi.org/10.1142/s0217984915501043.

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In this paper, we propose a novel scheme for controlling the group velocity of transmitted and reflected pulse from defect medium doped with four-level InGaN/GaN quantum dot nanostructure. Quantum dot nanostructure is designed numerically by Schrödinger and Poisson equations which solve self consistently. By size control of quantum dot and external voltage, one can design a four-level quantum dot with appropriate energy levels which can be suitable for controlling the group velocity of pulse transmission and reflection from defect slab with terahertz signal field. It is found that in the presence and absence of terahertz signal field the behaviors of transmission and reflection pulses are completely different. Moreover, it is shown that for strong terahertz signal field, by changing the thickness of the slab, simultaneous peak and dip for transmission and reflection pulse are obtained.

28

Hasegawa, Takayuki, and Osamu Kojima. "Effects of electric field screening induced by photogenerated carriers on terahertz wave measurement in a GaAs epitaxial structure." Applied Physics Express 17, no. 5 (May 1, 2024): 051006. http://dx.doi.org/10.35848/1882-0786/ad3ee1.

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Abstract In this work we investigate the effects of electric field screening induced by photogenerated carriers on terahertz wave radiation originating from transient phenomena in the electric field region of a GaAs epitaxial structure. The transient-phenomena excitation and timing of the screening are individually controlled by a pair of ultrashort optical pulses separated by a time interval. Under the condition that the preceding pulse is intensity-modulated by an optical chopper and is irradiated to the sample, the amplitude of the terahertz wave generated by the subsequent pulse is modulated. This result originates from electric field modulation by photogenerated carriers in the preceding pulse.

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Zvezdin, A. K., R. M. Dubrovin, and A. V. Kimel. "Giant Parametric Amplification of the Inverse Cotton–Mouton Effect in Antiferromagnetic Crystals." JETP Letters 119, no. 5 (March 2024): 363–71. http://dx.doi.org/10.1134/s0021364023604050.

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The interaction of light with spins in a Heisenberg antiferromagnet with a negligibly low magnetic anisotropy as in RbMnF3 has been theoretically analyzed. In particular, an optical pump–probe experiment, where coherent terahertz magnons are excited by short pump laser pulses in the antiferromagnet and are then detected by a probe pulse delayed with respect to the pump pulse, has been simulated. It has been shown that the giant increase in the intensity of excitation of terahertz magnons under the influence of the inverse Cotton–Mouton effect occurs near parametric resonance, i.e., in the parametric instability region.

30

Sazonov, S. V., and N. V. Ustinov. "Soliton mode of terahertz radiation generation using picosecond laser pulses with tilted wave fronts." Laser Physics Letters 19, no. 2 (January 20, 2022): 025401. http://dx.doi.org/10.1088/1612-202x/ac4914.

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Abstract The soliton-like mode for highly efficient generation of terahertz radiation in a quadratically nonlinear medium by means of optical pulses with tilted wave fronts is investigated. For optical and terahertz pulses, a system of the Zakharov–Boussinesq type equations describing the process of generation at arbitrary angles of the tilt of wave fronts is derived. Various cases of the soliton generation are analyzed. It is shown that the tilt of wave fronts is fundamental for the formation of the optical-terahertz solitons of a new type, which we call dispersionless solitons.

31

Emelina, Anna, Ivan Laryushin, and Alexander Romanov. "Dynamics of Gas Ionization by Laser Pulses with Different Envelope Shapes." Photonics 10, no. 5 (April 26, 2023): 499. http://dx.doi.org/10.3390/photonics10050499.

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The properties of the dynamics of gas ionization under the action of femtosecond ionizing laser pulses with various envelope shapes are studied. It is shown that the duration of ionization in the saturation regime (at a high final degree of ionization) can either increase or decrease with an increase in the peak intensity of the ionizing pulse, depending on the shape of its envelope. We also determined the influence of the pulse shape on the spectrum of Brunel harmonics and the terahertz yield when two-color pulses are used.

32

Partini, Juliasih, Kamsul Abraha, Arief Hermanto, Satoshi Tomita, and Matsui Takahiro. "Terahertz Signal Measurement on a Chiral Metamaterial Using Terahertz Emission Spectroscopy." Applied Mechanics and Materials 771 (July 2015): 125–28. http://dx.doi.org/10.4028/www.scientific.net/amm.771.125.

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Terahertz Signal generated from chiral metamaterial due to the second order non-linear process has been observed. Chiral metamaterial used in this research have a periodic square pattern with different depth on a silver film and was fabricated by Focused Ion Beam System. Terahertz emission spectroscopy has been conducted using two amplified 100 fs laser pulses with a central wavelength of 800 nm. The emission will emerge due to an optical rectification process as a result of an intense femtosecond laser pulses radiation on a chiral metamaterial sample. The measurement result clearly shows that the terahertz signal is emitted at 2 THz frequency and sufficiently fit with a square of laser power, which is consistent with an expected optical rectification process.

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Wei, Yuxuan, Jiaming Le, Li Huang, and Chuanshan Tian. "Efficient generation of intense broadband terahertz pulses from quartz." Applied Physics Letters 122, no. 8 (February 20, 2023): 081105. http://dx.doi.org/10.1063/5.0134139.

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Intense terahertz (THz) pulses facilitate the observation of various nonlinear optical effects and the manipulation of material properties. In this work, we report a convenient approach to produce strong broadband THz pulses with a center frequency tunable between 2 and 4 THz. A coherent THz light source with a pulse energy of 1.2 mJ can be generated from low-cost crystalline quartz using a tilted-pulse-front scheme. Thanks to the wide transparent spectral window and high damage threshold, our theoretical analysis and experiment show that the THz conversion efficiency in quartz reaches 0.05%, which is comparable with that in LiNbO3 at room temperature, while the output THz spectral range is much broader in the former. This work not only provides the light source that is urgently needed for nonlinear THz spectroscopy beyond 2 THz but also offers an alternative route in selecting nonlinear optical crystals for optical frequency conversion.

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Bogatskaya A.V., Volkova E.A., and Popov A. M. "Self-consistent three-dimensional model of ultrashort terahertz pulse amplification in a laser-induced nonequilibrium plasma channel in xenon." Optics and Spectroscopy 130, no. 12 (2022): 1591. http://dx.doi.org/10.21883/eos.2022.12.55247.48-22.

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The propagation and amplification of ultrashort terahertz pulses in a nonequilibrium photoionization plasma channel formed in xenon by a powerful femtosecond UV laser pulse is studied in three-dimensional geometry. The study is based on the self-consistent numerical integration of the second-order wave equation in cylindrical geometry and the Boltzmann kinetic equation in the two-term expansion to describe the electron velocity distribution function in the spatially inhomogeneous nonequilibrium plasma of the channel. Keywords: nonlinear optics, terahertz radiation, nonequilibrium plasma channel, numerical simulation.

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Krotkus, Arūnas, Ignas Nevinskas, and Ričardas Norkus. "Semiconductor Characterization by Terahertz Excitation Spectroscopy." Materials 16, no. 7 (April 3, 2023): 2859. http://dx.doi.org/10.3390/ma16072859.

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Surfaces of semiconducting materials excited by femtosecond laser pulses emit electromagnetic waves in the terahertz (THz) frequency range, which by definition is the 0.1–10 THz region. The nature of terahertz radiation pulses is, in the majority of cases, explained by the appearance of ultrafast photocurrents. THz pulse duration is comparable with the photocarrier momentum relaxation time, thus such hot-carrier effects as the velocity overshoot, ballistic carrier motion, and optical carrier alignment must be taken into consideration when explaining experimental observations of terahertz emission. Novel commercially available tools such as optical parametric amplifiers that are capable of generating femtosecond optical pulses within a wide spectral range allow performing new unique experiments. By exciting semiconductor surfaces with various photon energies, it is possible to look into the ultrafast processes taking place at different electron energy levels of the investigated materials. The experimental technique known as the THz excitation spectroscopy (TES) can be used as a contactless method to study the band structure and investigate the ultrafast processes of various technologically important materials. A recent decade of investigations with the THz excitation spectroscopy method is reviewed in this article. TES experiments performed on the common bulk A3B5 compounds such as the wide-gap GaAs, and narrow-gap InAs and InSb, as well as Ge, Te, GaSe and other bulk semiconductors are reviewed. Finally, the results obtained by this non-contact technique on low-dimensional materials such as ultrathin mono-elemental Bi films, InAs, InGaAs, and GaAs nanowires are also presented.

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Opromolla, Michele, and Vittoria Petrillo. "Two-Color TeraHertz Radiation by a Multi-Pass FEL Oscillator." Applied Sciences 11, no. 14 (July 14, 2021): 6495. http://dx.doi.org/10.3390/app11146495.

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In this paper, we show that an electron beam produced by a super-conducting linac, driven in a sequence of two undulator modules of different periods, can generate two-color Terahertz radiation with wavelengths ranging from 100 μm to 2 μm. The generated pulses are synchronized, both MW-class, and highly coherent. Their specific properties and generation will be discussed in detail. Besides the single-spike pulse structure, usually observed in oscillators, we show that both the THz pump and probe can be modulated in a coherent comb of pulses, enabling periodic excitation and stroboscopic measurements.

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Gong, Peng Wei, Zhe Ma, Hong Mei Ma, and Chun Tao Yang. "Experimental Investigation of Terahertz Temporal Response of a Photoconductive Switch." Advanced Materials Research 571 (September 2012): 491–95. http://dx.doi.org/10.4028/www.scientific.net/amr.571.491.

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Picosecond or subpicosecond electrical pulses can be generated from femtosecond laser excited photoconductive switches, and this technique is an effective method to characterize the rise time of the broadband oscilloscopes recently. In this paper, low temperature grown GaAs (LT-GaAs) is used as the substrate of the photoconductive switch which is excited by the femtosecond laser. After propagating along a coplanar waveguide, the generated terahertz pulses are transferred to a 1.85 mm coaxial cable through a microwave probe. The pulse width is measured in a 70 GHz sampling oscilloscope, the FWHM value is about 7.4 ps.

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Wang, Bo, Gaoshuai Wei, Jianing Chen, and Li Wang. "Terahertz response of ultrafast spin polarization in semi-insulating GaAs." Applied Physics Letters 121, no. 2 (July 11, 2022): 021101. http://dx.doi.org/10.1063/5.0099739.

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Due to its high sensitivity and time-resolved ability, terahertz time-domain spectroscopy is a powerful tool for investigating ultrafast carrier dynamics in semiconductors. In addition to charges, spins of ultrafast carriers provide an alternate degree of freedom to design modern electronic devices but are rarely studied by terahertz time-domain spectroscopy. Here, ultrafast spin polarization in semi-insulating GaAs is studied by optical-pump terahertz-probe experiments at room temperature. We used circularly and linearly polarized femtosecond laser pulses to inject nonequilibrium carriers in GaAs and observed that both the transmitted and reflected terahertz signals exhibited different dynamical evolutions under the excitations of linearly and circularly polarized laser pulses, which are ascribed to the generation and relaxation of spin-polarized electrons. The lifetime of the ultrafast spin polarization was obtained from our experiments, highlighting the potentialities of terahertz spectroscopy for the investigation of spin relaxation in semiconductors.

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Chefonov, O. V., A. V. Ovchinnikov, and M. B. Agranat. "Study of second optical harmonic generation in terahertz pulse-induced antiferromagnetic NiO." Quantum Electronics 52, no. 3 (March 1, 2022): 269–73. http://dx.doi.org/10.1070/qel17996.

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Abstract Intense terahertz pulses and a process of second harmonic generation are promising methods for exciting and studying an ultrafast dynamic response in magnetically ordered systems, ferroelectrics, and multiferroics on the picosecond time scale. In the present work, we report experimental results on generation of second optical harmonic in centrosymmetric antiferromagnetic NiO induced by intense terahertz pulses with an electric field strength of up to 20 MV cm−1.

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Katayama, Ikufumi, Hiroki Kawakami, Kotaro Araki, Yusuke Arashida, Yasuo Minami, Lie-Wei Nien, Orjan Sele Handegard, Tadaaki Nagao, Masahiro Kitajima, and Jun Takeda. "Ultrafast carrier generation in Bi1-xSbx thin films induced by intense monocycle terahertz pulses." EPJ Web of Conferences 205 (2019): 04016. http://dx.doi.org/10.1051/epjconf/201920504016.

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Using terahertz-pump and terahertz-probe spectroscopy, we investigated terahertz-induced carrier generation processes in Bi1-xSbx thin films. The field dependence of the terahertz-induced transmittance change indicates distinct nonlinearity related to the Zener tunneling in narrow band-gap materials.

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Verma, N. K., and P. Jha. "Enhanced terahertz radiation generation by two-color laser pulses propagating in plasma." Laser and Particle Beams 34, no. 2 (April 29, 2016): 378–83. http://dx.doi.org/10.1017/s0263034616000173.

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AbstractA one-dimensional (1D) numerical model for studying enhanced terahertz (THz) radiation generation by mixing of ordinary and extraordinary modes of two-color laser pulses propagating in magnetized plasma has been presented. The direction of the static external magnetic field is such that one of the two laser pulses propagates in the extraordinary mode, while the other pulse propagates in the ordinary mode, through homogeneous plasma. A transverse electromagnetic wave with frequency in the THz range is generated due to the presence of the external magnetic field. It is observed that larger amplitude THz radiation can be generated by mixing of the ordinary and extraordinary modes of the two-color laser pulses as compared with the single laser pulse propagating in the extraordinary mode. Further, 2D simulations using the XOOPIC code show that the fields obtained via simulation study are compatible with those obtained from the numerical model.

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Karushkin, Nikolai, and Ilya Obukhov. "Nanophoton Generator of Picosecond Pulses." Infocommunications and Radio Technologies 5, no. 2 (October 7, 2022): 169–84. http://dx.doi.org/10.29039/2587-9936.2022.05.2.12.

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Results of theoretical analyses of possibility of generations of periodic picosecond pulses of voltage are presented. This process is possible under condition of external electromagnetic radiation only. As an active element of such generator may be heterojunction in which the relaxation instability of electron concentration is developed. The possible variant of heterostructure and its static and time depended electric characteristics are demonstrated. Parameters of heterostructure and operating regimes can be select so that pulses of voltage will be in terahertz range.

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Tanaka, K. "Nonlinear Terahertz Spectroscopy in Solids with Single-Cycle Terahertz Pulses." EPJ Web of Conferences 41 (2013): 09015. http://dx.doi.org/10.1051/epjconf/20134109015.

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Bostak, J. S., D. W. van der Weide, D. M. Bloom, B. A. Auld, and E. Özbay. "All-electronic terahertz spectroscopy system with terahertz free-space pulses." Journal of the Optical Society of America B 11, no. 12 (December 1, 1994): 2561. http://dx.doi.org/10.1364/josab.11.002561.

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Гинзбург, Н. С., Л. А. Юровский, А. В. Назаровский, А. С. Сергеев, and И. В. Зотова. "Генерация импульсов сверхизлучения терагерцового диапазона в процессе вынужденного рассеяния лазерного излучения на попутном сильноточном релятивистском электронном пучке." Журнал технической физики 46, no. 23 (2020): 8. http://dx.doi.org/10.21883/pjtf.2020.23.50339.18479.

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The possibility of generation of terahertz superradiance (SR) pulses in the case of incidental scattering of a laser pulse by a high-current relativistic electron beam with frequency conversion down is analyzed. Scattered radiation propagates in the opposite direction (with respect to the translational velocity of the particles). It is shown that when using pulses with an energy of 3 kJ at a wavelength of 1 μm as a pump during optimization of the laser pulse duration and the length of the interaction region, it is possible to generate pulses of scattered counter (relative to the translational particle velocity) radiation with a power of the order of 580 kW and a duration of 30 ps at a wavelength of 100 μm.

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Voevodin, Vladimir, Svetlana Bereznaya, Yury S. Sarkisov, Nikolay N. Yudin, and Sergey Yu Sarkisov. "Terahertz Generation by Optical Rectification of 780 nm Laser Pulses in Pure and Sc-Doped ZnGeP2 Crystals." Photonics 9, no. 11 (November 16, 2022): 863. http://dx.doi.org/10.3390/photonics9110863.

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Terahertz wave generation through the optical rectification of 780 nm femtosecond laser pulses in ZnGeP2 crystals has been studied. All of the possible interactions of types I and II were analyzed by modeling and experimentally. We demonstrate the possibility of broadband “low-frequency” terahertz generation by an ee–e interaction (with two pumping waves and a generated terahertz wave; all of these had extraordinary polarization in the crystal) and “high-frequency” terahertz generation by an oe–e interaction. The arising possibility of achieving the narrowing of the terahertz generation bandwidth at the oe–e interaction using thicker ZnGeP2 crystals is experimentally confirmed. It has been found that the thermal annealing of as-grown ZnGeP2 crystals and their doping with a 0.01 mass % of Sc reduces the absorption in the “anomalous absorption” region (λ = 0.62–3 μm). The terahertz generation by the oo–e interaction in (110) ZnGeP2:Sc and the as-grown ZnGeP2 crystals of equal thicknesses was compared. It has been found that ZnGeP2:Sc is more efficient for 780 nm femtosecond laser pulses optical rectification.

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Huang, Ruixuan, Haoran Zhang, Weiwei Li, Zhigang He, Lin Wang, Qika Jia, and Yalin Lu. "Proposition of a femtosecond pulse radiolysis with terahertz probe pulses." Radiation Physics and Chemistry 157 (April 2019): 28–32. http://dx.doi.org/10.1016/j.radphyschem.2018.12.004.

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Li, Hang, Ping Chen, Jin-Shou Tian, Yan-Hua Xue, Jun-Feng Wang, Yong-Sheng Gou, Min-Rui Zhang, et al. "High time-resolution detector based on THz pulse accelerating and scanning electron beam." Acta Physica Sinica 71, no. 2 (2022): 028501. http://dx.doi.org/10.7498/aps.71.20210871.

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Terahertz pulses accelerating and scanning electron beam can break through the limitation of accelerating electric field between cathodes and grids in traditional streak tubes, thus reducing the time dispersion and enhancing the temporal resolution of time-scanning detectors. Based on this new technology, in this paper an ultra-small structured time-resolved detector with no focusing pole is designed. The terahertz pulse coupling/enhancing device suitable for acceleration zone and scanning zone is designed and optimized. The enhanced coefficient of the terahertz pulse electric field in the device reaches 9.39. In the paper, the relationship between time dispersion in acceleration zone and the moment of electrons emission is analyzed theoretically. We also analyze the influence of space charge effect on time dispersion. The electronic trajectory tracking is used to calculate and analyze the time dispersion of this detector, and finally the time resolution is better than 50fs.

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Yano, Kaori, and Toshiaki Hattori. "Improving a Terahertz Time-Domain Spectroscopy Apparatus Using Neodymium Magnets." International Letters of Chemistry, Physics and Astronomy 62 (November 2015): 10–14. http://dx.doi.org/10.18052/www.scipress.com/ilcpa.62.10.

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The signal-to-noise ratio obtained from terahertz time-domain spectroscopy is significantly affected by the low available power of terahertz waves. We constructed a terahertz-wave source with emission power enhanced by a magnetic field. The emitter is composed of an InAs wafer and two neodymium magnets. The emitter was irradiated by femtosecond laser pulses. The data quality of terahertz spectroscopic measurements was evaluated, and reduction of error in the data obtained due to the terahertz power enhancement was observed.

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Yano, Kaori, and Toshiaki Hattori. "Improving a Terahertz Time-Domain Spectroscopy Apparatus Using Neodymium Magnets." International Letters of Chemistry, Physics and Astronomy 62 (November 27, 2015): 10–14. http://dx.doi.org/10.56431/p-cw453x.

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The signal-to-noise ratio obtained from terahertz time-domain spectroscopy is significantly affected by the low available power of terahertz waves. We constructed a terahertz-wave source with emission power enhanced by a magnetic field. The emitter is composed of an InAs wafer and two neodymium magnets. The emitter was irradiated by femtosecond laser pulses. The data quality of terahertz spectroscopic measurements was evaluated, and reduction of error in the data obtained due to the terahertz power enhancement was observed.

Journal articles on the topic 'Terahertz pulses'

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