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Sekiguchi F, Budzinauskas K, Padmanabhan P, Versteeg RB, Tsurkan V, Kézsmárki I, Foggetti F, Artyukhin S, van Loosdrecht PHM. Slowdown of photoexcited spin dynamics in the non-collinear spin-ordered phases in skyrmion host GaV 4S 8. Nat Commun 2022; 13:3212. [PMID: 35680864 PMCID: PMC9184521 DOI: 10.1038/s41467-022-30829-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Accepted: 05/20/2022] [Indexed: 11/10/2022] Open
Abstract
Formation of magnetic order alters the character of spin excitations, which then affects transport properties. We investigate the photoexcited ultrafast spin dynamics in different magnetic phases in Néel-type skyrmion host GaV4S8 with time-resolved magneto-optical Kerr effect experiments. The coherent spin precession, whose amplitude is enhanced in the skyrmion-lattice phase, shows a signature of phase coexistence across the magnetic phase transitions. The incoherent spin relaxation dynamics slows down by a factor of two in the skyrmion-lattice/cycloid phases, indicating significant decrease in thermal conductivity triggered by a small change of magnetic field. The slow heat diffusion in the skyrmion-lattice/cycloid phases is attributed to the stronger magnon scattering off the domain walls formed in abundance in the skyrmion-lattice/cycloid phase. These results highlight the impact of spatial spin structure on the ultrafast heat transport in spin systems, providing a useful insight for the step toward ultrafast photocontrol of the magnets with novel spin orders. Skyrmions are a topological magnetic texture that have garnered considerable interest for various technological applications. Here, Sekiguchi et al. investigate the ultrafast optical response of GaV4S6, and find a significant reduction in the thermal conductivity in the skyrmion phase.
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Affiliation(s)
- Fumiya Sekiguchi
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, D-50937, Köln, Germany.
| | - Kestutis Budzinauskas
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, D-50937, Köln, Germany
| | - Prashant Padmanabhan
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, D-50937, Köln, Germany
| | - Rolf B Versteeg
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, D-50937, Köln, Germany
| | - Vladimir Tsurkan
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159, Augsburg, Germany.,Institute of Applied Physics, MD 2028, Chișinău, Republic of Moldova
| | - István Kézsmárki
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159, Augsburg, Germany
| | - Francesco Foggetti
- Istituto Italiano di Tecnologia, Via Morego 30, 16163, Genova, Italy.,Dipartimento di Fisica, Università di Genova, Via Dodecaneso, 33, 16146, Genova, Italy
| | - Sergey Artyukhin
- Istituto Italiano di Tecnologia, Via Morego 30, 16163, Genova, Italy
| | - Paul H M van Loosdrecht
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, D-50937, Köln, Germany.
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2
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Saito Y, Mikhaylovskiy RV. Modelling nonlocal nonlinear spin dynamics in antiferromagnetic orthoferrites. Faraday Discuss 2022; 237:381-388. [PMID: 35697343 PMCID: PMC9477181 DOI: 10.1039/d2fd00035k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Excitation with an ultrashort light pulse is arguably the only way to control spins in antiferromagnetic materials at both the nanoscale in space and ultrafast time scale. While recent experiments highlighted tantalising opportunities for spin switching and magnonics in antiferromagnets, the theoretical description of antiferromagnetic spin dynamics driven by strongly localised and ultrashort excitation is in its infancy. Here we report a theoretical model describing the nonlocal and nonlinear spin response to the excitation by light. We show that strongly localised ultrafast excitation can drive spin switching, which propagates in space and acts as a source of spin waves. Our theoretical formalism is readily available to describe current and future ultrafast spectroscopy experiments in antiferromagnets. We calculate nonlinear magnetic dynamics induced by an intense THz pulse in an antiferromagnet. As a result, we reveal an inhomogeneous switching regime involving moving domain walls and propagating magnons.![]()
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Affiliation(s)
- Yuichi Saito
- Department of Physics, Lancaster University, Bailrigg, Lancaster LA1 4YW, UK.
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3
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Iba A, Ikeda M, Agulto VC, Mag-usara VK, Nakajima M. A Study of Terahertz-Wave Cylindrical Super-Oscillatory Lens for Industrial Applications. SENSORS (BASEL, SWITZERLAND) 2021; 21:6732. [PMID: 34695944 PMCID: PMC8541439 DOI: 10.3390/s21206732] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Revised: 09/22/2021] [Accepted: 10/07/2021] [Indexed: 11/21/2022]
Abstract
This paper describes the design and development of a cylindrical super-oscillatory lens (CSOL) for applications in the sub-terahertz frequency range, which are especially ideal for industrial inspection of films using terahertz (THz) and millimeter waves. Product inspections require high resolution (same as inspection with visible light), long working distance, and long depth of focus (DOF). However, these are difficult to achieve using conventional THz components due to diffraction limits. Here, we present a numerical approach in designing a 100 mm × 100 mm CSOL with optimum properties and performance for 0.1 THz (wavelength λ = 3 mm). Simulations show that, at a focal length of 70 mm (23.3λ), the focused beam by the optimized CSOL is a thin line with a width of 2.5 mm (0.84λ), which is 0.79 times the diffraction limit. The DOF of 10 mm (3.3λ) is longer than that of conventional lenses. The results also indicate that the generation of thin line-shaped focal beam is dominantly influenced by the outer part of the lens.
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Affiliation(s)
- Ayato Iba
- Institute of Laser Engineering, Osaka University, Osaka 565-0871, Japan; (A.I.); (V.C.A.); (V.K.M.-u.)
- Asahi Kasei Corporation, Shizuoka 416-8501, Japan;
| | - Makoto Ikeda
- Asahi Kasei Corporation, Shizuoka 416-8501, Japan;
| | - Verdad C. Agulto
- Institute of Laser Engineering, Osaka University, Osaka 565-0871, Japan; (A.I.); (V.C.A.); (V.K.M.-u.)
| | - Valynn Katrine Mag-usara
- Institute of Laser Engineering, Osaka University, Osaka 565-0871, Japan; (A.I.); (V.C.A.); (V.K.M.-u.)
| | - Makoto Nakajima
- Institute of Laser Engineering, Osaka University, Osaka 565-0871, Japan; (A.I.); (V.C.A.); (V.K.M.-u.)
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4
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Iba A, Domier CW, Ikeda M, Mase A, Nakajima M, Pham AV, Luhmann NC. Subdiffraction focusing with a long focal length using a terahertz-wave super-oscillatory lens. OPTICS LETTERS 2021; 46:4912-4915. [PMID: 34598232 DOI: 10.1364/ol.434825] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Accepted: 09/07/2021] [Indexed: 06/13/2023]
Abstract
This Letter describes a super-oscillatory lens (SOL), with concentric ring-type metallic slits photolithographically fabricated on a glass substrate, that can function at subterahertz frequencies. The SOL has been investigated both experimentally and theoretically and demonstrates a spatial resolution of 1.5 mm (0.5λ), which is 0.45 times the diffraction limit, with a focal length of 75 mm (25λ) at 100 GHz (λ=3mm). Furthermore, the depth of focus of the lens was measured to be 47 mm, which is 10.8 times larger than that of a conventional lens. This type of SOL, with subdiffraction focusing, is thus highly effective for use in industrial inspections with millimeter and terahertz waves.
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5
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Agulto VC, Iwamoto T, Kitahara H, Toya K, Mag-Usara VK, Imanishi M, Mori Y, Yoshimura M, Nakajima M. Terahertz time-domain ellipsometry with high precision for the evaluation of GaN crystals with carrier densities up to 10 20 cm -3. Sci Rep 2021; 11:18129. [PMID: 34526558 PMCID: PMC8443745 DOI: 10.1038/s41598-021-97253-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Accepted: 08/20/2021] [Indexed: 01/09/2023] Open
Abstract
Gallium nitride (GaN) is one of the most technologically important semiconductors and a fundamental component in many optoelectronic and power devices. Low-resistivity GaN wafers are in demand and actively being developed to improve the performance of vertical GaN power devices necessary for high-voltage and high-frequency applications. For the development of GaN devices, nondestructive characterization of electrical properties particularly for carrier densities in the order of 1019 cm-3 or higher is highly favorable. In this study, we investigated GaN single crystals with different carrier densities of up to 1020 cm-3 using THz time-domain ellipsometry in reflection configuration. The p- and s-polarized THz waves reflected off the GaN samples are measured and then corrected based on the analysis of multiple waveforms measured with a rotating analyzer. We show that performing such analysis leads to a ten times higher precision than by merely measuring the polarization components. As a result, the carrier density and mobility parameters can be unambiguously determined even at high conductivities.
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Affiliation(s)
- Verdad C Agulto
- Institute of Laser Engineering, Osaka University, Suita, Osaka, 565-0871, Japan
| | | | - Hideaki Kitahara
- Institute of Laser Engineering, Osaka University, Suita, Osaka, 565-0871, Japan
| | - Kazuhiro Toya
- Institute of Laser Engineering, Osaka University, Suita, Osaka, 565-0871, Japan
| | | | - Masayuki Imanishi
- Graduate School of Engineering, Osaka University, Suita, Osaka, 565-0871, Japan
| | - Yusuke Mori
- Graduate School of Engineering, Osaka University, Suita, Osaka, 565-0871, Japan
| | - Masashi Yoshimura
- Institute of Laser Engineering, Osaka University, Suita, Osaka, 565-0871, Japan
| | - Makoto Nakajima
- Institute of Laser Engineering, Osaka University, Suita, Osaka, 565-0871, Japan.
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6
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Fitzky G, Nakajima M, Koike Y, Leitenstorfer A, Kurihara T. Ultrafast Control of Magnetic Anisotropy by Resonant Excitation of 4f Electrons and Phonons in Sm_{0.7}Er_{0.3}FeO_{3}. PHYSICAL REVIEW LETTERS 2021; 127:107401. [PMID: 34533346 DOI: 10.1103/physrevlett.127.107401] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2021] [Accepted: 07/28/2021] [Indexed: 06/13/2023]
Abstract
We compare the ultrafast dynamics of the spin reorientation transition in the orthoferrite Sm_{0.7}Er_{0.3}FeO_{3} following two different pumping mechanisms. Intense few-cycle pulses in the midinfrared selectively excite either the f-f electronic transition of Sm^{3+} or optical phonons. With phonon pumping, a finite time delay exists for the spin reorientation, reflecting the energy transfer between the lattice and 4f system. In contrast, an instantaneous response is found for resonant f-f excitation. This suggests that 4f electronic pumping can directly alter the magnetic anisotropy due to the modification of 4f-3d exchange at femtosecond timescales, without involving lattice thermalization.
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Affiliation(s)
- Gabriel Fitzky
- Department of Physics and Center for Applied Photonics, University of Konstanz, D-78457 Konstanz, Germany
| | - Makoto Nakajima
- Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Yohei Koike
- Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Alfred Leitenstorfer
- Department of Physics and Center for Applied Photonics, University of Konstanz, D-78457 Konstanz, Germany
| | - Takayuki Kurihara
- Department of Physics and Center for Applied Photonics, University of Konstanz, D-78457 Konstanz, Germany
- Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8581, Japan
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7
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Wang L, Xiao R, Yang S, Qiu H, Shen Z, Lv P, Zhang C, Hu W, Nakajima M, Jin B, Lu Y. 3D porous graphene-assisted capsulized cholesteric liquid crystals for terahertz power visualization. OPTICS LETTERS 2020; 45:5892-5895. [PMID: 33057312 DOI: 10.1364/ol.405695] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Accepted: 09/22/2020] [Indexed: 06/11/2023]
Abstract
We demonstrate a high-efficiency visualized terahertz (THz) power meter based on the THz-photothermochromism of capsulized cholesteric liquid crystals (CCLCs) embedded in three-dimensional porous graphene (3DPG). The graphene is a broadband perfect absorber for THz radiation and transfers heat efficiently, and its black background is beneficial for color measurement. Quantitative visualization of THz intensity up to 2.8×102mW/cm2 is presented. The minimal detectable THz power is 0.009 mW. With multi-microcapsule analysis, the relationship between THz power and the average hue value of CCLCs achieves linearity. The device can convert THz radiation to visible light and is lightweight, cheap, and easy to use.
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Arikawa Y, Ota M, Nakajima M, Shimizu T, Segawa S, Khoa Phan TN, Sakawa Y, Abe Y, Morace A, Mirfayzi SR, Yogo A, Fujioka S, Nakai M, Shiraga H, Azechi H, Kodama R, Kan K, Frenje J, Gatu Johnson M, Bose A, Kabadi NV, Sutcliffe GD, Adrian P, Li C, Séguin FH, Petrasso R. The conceptual design of 1-ps time resolution neutron detector for fusion reaction history measurement at OMEGA and the National Ignition Facility. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2020; 91:063304. [PMID: 32611003 DOI: 10.1063/1.5143657] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/26/2019] [Accepted: 05/05/2020] [Indexed: 06/11/2023]
Abstract
The nuclear burn history provides critical information about the dynamics of the hot-spot formation and high-density fuel-shell assembly of an Inertial Confinement Fusion (ICF) implosion, as well as information on the impact of alpha heating, and a multitude of implosion failure mechanisms. Having this information is critical for assessing the energy-confinement time τE and performance of an implosion. As the confinement time of an ICF implosion is a few tens of picoseconds, less than 10-ps time resolution is required for an accurate measurement of the nuclear burn history. In this study, we propose a novel 1-ps time-resolution detection scheme based on the Pockels effect. In particular, a conceptual design for the experiment on the National Ignition Facility and OMEGA are elaborated upon herein. A small organic Pockels crystal "DAST" is designed to be positioned ∼5 mm from the ICF implosion, which is scanned by a chirped pulse generated by a femto-second laser transmitted through a polarization-maintained optical fiber. The originally linearly polarized laser is changed to an elliptically polarized laser by the Pockels crystal when exposed to neutrons, and the modulation of the polarization will be analyzed. Our study using 35-MeV electrons showed that the system impulse response is 0.6 ps. The response time is orders of magnitude shorter than current systems. Through measurements of the nuclear burn history with unprecedented time resolution, this system will help for a better understanding of the dynamics of the hot-spot formation, high-density fuel-shell assembly, and the physics of thermonuclear burn wave propagation.
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Affiliation(s)
- Yasunobu Arikawa
- Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Masato Ota
- Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Makoto Nakajima
- Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Tomoki Shimizu
- Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Sadashi Segawa
- Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Thanh Nhat Khoa Phan
- Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Youichi Sakawa
- Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Yuki Abe
- Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Alessio Morace
- Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Seyed Reza Mirfayzi
- Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Akifumi Yogo
- Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Shinsuke Fujioka
- Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Mitsuo Nakai
- Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Hiroyuki Shiraga
- Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Hiroshi Azechi
- Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Ryosuke Kodama
- Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Koichi Kan
- The Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan
| | - Johan Frenje
- Plasma Science and Fusion Center at Massachusetts Institute of Technology, 77 Massachusetts Avenue, NW16, Cambridge, Massachusetts 02139-4307, USA
| | - Maria Gatu Johnson
- Plasma Science and Fusion Center at Massachusetts Institute of Technology, 77 Massachusetts Avenue, NW16, Cambridge, Massachusetts 02139-4307, USA
| | - Arijit Bose
- Plasma Science and Fusion Center at Massachusetts Institute of Technology, 77 Massachusetts Avenue, NW16, Cambridge, Massachusetts 02139-4307, USA
| | - Neel V Kabadi
- Plasma Science and Fusion Center at Massachusetts Institute of Technology, 77 Massachusetts Avenue, NW16, Cambridge, Massachusetts 02139-4307, USA
| | - Graeme D Sutcliffe
- Plasma Science and Fusion Center at Massachusetts Institute of Technology, 77 Massachusetts Avenue, NW16, Cambridge, Massachusetts 02139-4307, USA
| | - Patrick Adrian
- Plasma Science and Fusion Center at Massachusetts Institute of Technology, 77 Massachusetts Avenue, NW16, Cambridge, Massachusetts 02139-4307, USA
| | - Chikang Li
- Plasma Science and Fusion Center at Massachusetts Institute of Technology, 77 Massachusetts Avenue, NW16, Cambridge, Massachusetts 02139-4307, USA
| | - Fredrick H Séguin
- Plasma Science and Fusion Center at Massachusetts Institute of Technology, 77 Massachusetts Avenue, NW16, Cambridge, Massachusetts 02139-4307, USA
| | - Richard Petrasso
- Plasma Science and Fusion Center at Massachusetts Institute of Technology, 77 Massachusetts Avenue, NW16, Cambridge, Massachusetts 02139-4307, USA
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9
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Reconfiguration of magnetic domain structures of ErFeO 3 by intense terahertz free electron laser pulses. Sci Rep 2020; 10:7321. [PMID: 32355246 PMCID: PMC7193561 DOI: 10.1038/s41598-020-64147-5] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2019] [Accepted: 04/13/2020] [Indexed: 11/14/2022] Open
Abstract
Understanding the interaction between intense terahertz (THz) electromagnetic fields and spin systems has been gaining importance in modern spintronics research as a unique pathway to realize ultrafast macroscopic magnetization control. In this work, we used intense THz pulses with pulse energies in the order of 10 mJ/pulse generated from the terahertz free electron laser (THz-FEL) to irradiate the ferromagnetic domains of ErFeO3 single crystal. It was found that the domain shape can be locally reconfigured by irradiating the THz − FEL pulses near the domain boundary. Observed domain reconfiguration mechanism can be phenomenologically understood by the combination of depinning effect and the entropic force due to local thermal gradient exerted by terahertz irradiation. Our finding opens up a new possibility of realizing thermal-spin effects at THz frequency ranges by using THz-FEL pulses.
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10
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Wang L, Zhang Y, Guo X, Chen T, Liang H, Hao X, Hou X, Kou W, Zhao Y, Zhou T, Liang S, Yang Z. A Review of THz Modulators with Dynamic Tunable Metasurfaces. NANOMATERIALS 2019; 9:nano9070965. [PMID: 31266235 PMCID: PMC6669754 DOI: 10.3390/nano9070965] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Revised: 06/13/2019] [Accepted: 06/28/2019] [Indexed: 11/16/2022]
Abstract
Terahertz (THz) radiation has received much attention during the past few decades for its potential applications in various fields, such as spectroscopy, imaging, and wireless communications. To use terahertz waves for data transmission in different application systems, the efficient and rapid modulation of terahertz waves is required and has become an in-depth research topic. Since the turn of the century, research on metasurfaces has rapidly developed, and the scope of novel functions and operating frequency ranges has been substantially expanded, especially in the terahertz range. The combination of metasurfaces and semiconductors has facilitated both new opportunities for the development of dynamic THz functional devices and significant achievements in THz modulators. This paper provides an overview of THz modulators based on different kinds of dynamic tunable metasurfaces combined with semiconductors, two-dimensional electron gas heterostructures, superconductors, phase-transition materials, graphene, and other 2D material. Based on the overview, a brief discussion with perspectives will be presented. We hope that this review will help more researchers learn about the recent developments and challenges of THz modulators and contribute to this field.
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Affiliation(s)
- Lan Wang
- Terahertz Science Cooperative Innovation Center, School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chendu 610054, China
| | - Yaxin Zhang
- Terahertz Science Cooperative Innovation Center, School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chendu 610054, China.
| | - Xiaoqing Guo
- Terahertz Science Cooperative Innovation Center, School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chendu 610054, China
| | - Ting Chen
- Terahertz Science Cooperative Innovation Center, School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chendu 610054, China
| | - Huajie Liang
- Terahertz Science Cooperative Innovation Center, School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chendu 610054, China
| | - Xiaolin Hao
- Terahertz Science Cooperative Innovation Center, School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chendu 610054, China
| | - Xu Hou
- Terahertz Science Cooperative Innovation Center, School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chendu 610054, China
| | - Wei Kou
- Terahertz Science Cooperative Innovation Center, School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chendu 610054, China
| | - Yuncheng Zhao
- Terahertz Science Cooperative Innovation Center, School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chendu 610054, China
| | - Tianchi Zhou
- Terahertz Science Cooperative Innovation Center, School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chendu 610054, China
| | - Shixiong Liang
- National Key Laboratory of Application Specific Integrated Circuit, Hebei Semiconductor Research Institute, Shijiazhuang 050051, China
| | - Ziqiang Yang
- Terahertz Science Cooperative Innovation Center, School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chendu 610054, China.
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11
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Ohkoshi SI, Imoto K, Namai A, Yoshikiyo M, Miyashita S, Qiu H, Kimoto S, Kato K, Nakajima M. Rapid Faraday Rotation on ε-Iron Oxide Magnetic Nanoparticles by Visible and Terahertz Pulsed Light. J Am Chem Soc 2019; 141:1775-1780. [PMID: 30645116 DOI: 10.1021/jacs.8b12910] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Light- or electromagnetic wave-responsive magnetism is an attractive issue in spin chemistry and optical materials science. Herein we show the magnetization reversal induced by visible-light pulsed laser and the ultrafast dynamic magnetooptical effect caused by terahertz (THz) pulsed laser irradiation onto chemically synthesized magnetic films based on gallium-titanium-cobalt-substituted ε-Fe2O3 (GTC-ε-Fe2O3) and ε-Fe2O3 nanoparticles. Visible-light pulsed laser irradiation switches the sign of the Faraday effect in GTC-ε-Fe2O3 films. On the other hand, irradiating the ε-Fe2O3 film with pulsed THz light induces an ultrafast Faraday rotation in an extremely short time of 400 fs. The time evolution dynamics of these ultrafast magnetooptical effects are theoretically demonstrated by stochastic Landau-Lifshitz-Gilbert calculations of a nanoparticle model that considers all motions of the individual spins. These ε-iron oxide magnetic nanomaterials are expected to contribute to high-density magnetic memory media or high-speed operation circuit magnetic devices.
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Affiliation(s)
- Shin-Ichi Ohkoshi
- Department of Chemistry, School of Science , The University of Tokyo , 7-3-1 Hongo , Bunkyo-ku , Tokyo 113-0033 , Japan
| | - Kenta Imoto
- Department of Chemistry, School of Science , The University of Tokyo , 7-3-1 Hongo , Bunkyo-ku , Tokyo 113-0033 , Japan
| | - Asuka Namai
- Department of Chemistry, School of Science , The University of Tokyo , 7-3-1 Hongo , Bunkyo-ku , Tokyo 113-0033 , Japan
| | - Marie Yoshikiyo
- Department of Chemistry, School of Science , The University of Tokyo , 7-3-1 Hongo , Bunkyo-ku , Tokyo 113-0033 , Japan
| | - Seiji Miyashita
- Department of Physics, School of Science , The University of Tokyo , 7-3-1 Hongo , Bunkyo-ku , Tokyo 113-0033 , Japan
| | - Hongsong Qiu
- Institute of Laser Engineering , Osaka University , 2-6 Yamadaoka , Suita , Osaka 565-0871 , Japan
| | - Shodai Kimoto
- Institute of Laser Engineering , Osaka University , 2-6 Yamadaoka , Suita , Osaka 565-0871 , Japan
| | - Kosaku Kato
- Institute of Laser Engineering , Osaka University , 2-6 Yamadaoka , Suita , Osaka 565-0871 , Japan
| | - Makoto Nakajima
- Institute of Laser Engineering , Osaka University , 2-6 Yamadaoka , Suita , Osaka 565-0871 , Japan
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12
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Visible Measurement of Terahertz Power Based on Capsulized Cholesteric Liquid Crystal Film. APPLIED SCIENCES-BASEL 2018. [DOI: 10.3390/app8122580] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
We demonstrate a new method to detect terahertz (THz) power using a temperature-supersensitive capsulized cholesteric liquid crystal film based on the thermochromic and thermodiffusion effect, which is clearly observed. A quantitative visualization of the THz intensity up to 4.0 × 103 mW/cm2 is presented. The diameter of the color change area is linearly dependent on the THz radiation power above 0.07 mW in the steady state. Moreover, the THz power can be detected for 1 sec of radiation with a parabolic relation to the color change area. The THz power meter is robust, cost-effective, portable, and even flexible, and can be used in applications such as THz imaging, biological sensing, and inspection.
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Qiu H, Kurihara T, Harada H, Kato K, Takano K, Suemoto T, Tani M, Sarukura N, Yoshimura M, Nakajima M. Enhancing terahertz magnetic near field induced by a micro-split-ring resonator with a tapered waveguide. OPTICS LETTERS 2018; 43:1658-1661. [PMID: 29652333 DOI: 10.1364/ol.43.001658] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2018] [Accepted: 03/03/2018] [Indexed: 06/08/2023]
Abstract
Substantial enhancement of terahertz magnetic near field achieved by the combination of a tapered metallic waveguide and a micro-split-ring resonator is demonstrated. The magnetic near field is probed directly via the magneto-optic sampling with a Tb3Ga5O12 crystal. The incident terahertz wave with a half-cycle waveform is generated by using the pulse-front tilting method. The magnetic near field at the resonant frequency is enhanced by more than 30 times through the combination of the waveguide and the resonator. The peak amplitude of the magnetic field with a damped oscillation waveform in the time domain is up to 0.4 T. The resonant frequency can be tuned by adopting different resonator designs. The mechanism of the enhancement is analyzed by performing calculations based on the finite element method. The strong terahertz magnetic near field enables the excitation of large-amplitude spin dynamics and can be utilized for an ultrafast spin control.
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