A5027952155- Terahertz technology and applications
- Photonic and Optical Devices
- Semiconductor Quantum Structures and Devices
- Magnetic properties of thin films
- Spectroscopy and Laser Applications
- Photonic Crystals and Applications
- Metamaterials and Metasurfaces Applications
- Plasmonic and Surface Plasmon Research
- Gyrotron and Vacuum Electronics Research
- Superconducting and THz Device Technology
- Nonlinear Dynamics and Pattern Formation
- Advancements in Photolithography Techniques
- Spectroscopy and Quantum Chemical Studies
- Quantum and electron transport phenomena
- Solid-state spectroscopy and crystallography
- Microwave Engineering and Waveguides
- Topological Materials and Phenomena
- Phase-change materials and chalcogenides
- Fatigue and fracture mechanics
- Magneto-Optical Properties and Applications
- Luminescence Properties of Advanced Materials
- Transition Metal Oxide Nanomaterials
- Magnetism in coordination complexes
- Ga2O3 and related materials
- Laser-Matter Interactions and Applications
Keio University Hospital
2025
Osaka University
2015-2024
Nissan Chemical Corporation (Japan)
2007-2024
The University of Tokyo
2009-2024
Institute for Laser Technology
2015-2022
Tokyo University of Agriculture and Technology
2021
Tokyo Institute of Technology
2017-2021
Fukui University of Technology
2021
Suita Municipal Hospital
2019
Osaka Prefecture University
2018-2019
Magnetic ferrites such as Fe3O4 and Fe2O3 are extensively used in a range of applications because they inexpensive chemically stable. Here we show that rhodium-substituted ε-Fe2O3, ε-RhxFe2−xO3 nanomagnets prepared by nanoscale chemical synthesis using mesoporous silica template, exhibit huge coercive field (Hc) 27 kOe at room temperature. Furthermore, crystallographically oriented sample recorded an Hc value 31 kOe, which is the largest among metal-oxide-based magnets comparable to those...
Since the demonstration of p-type gallium nitride (GaN) through doping with substitutional magnesium (Mg) atoms
Millimeter waves (30−300 GHz) are starting to be used in next generation high-speed wireless communications. To avoid electromagnetic interference this communication, finding a suitable wave absorber the millimeter range is an urgent matter. In work, we prepared high-performance composed of series aluminum-substituted ε-iron oxide, ε-AlxFe2−xO3, nanomagnets (0 ≤ x 0.40) with particle size between 25 and 50 nm. The materials have orthorhombic crystal structure Pna21 space group, which has...
Coherent control of the precession motion magnetizations in a single crystal YFeO3 with double half-cycle pulse terahertz waves was demonstrated. Quasiferromagnetic (0.299 THz) and quasiantiferromagnetic (0.527 modes were selectively excited by choosing an appropriate interval two pulses observed as free induction decay (FID) signals from spin system. By observing circularly polarized FID due to ferromagnetic resonance, we also succeeded confirming directly energy storage system recovery...
Terahertz time domain spectroscopy was performed on orthoferrite ErFeO3. Through the emission from two magnetic resonance modes, we succeeded in observing spin reorientation transition. Depending orientation of single crystal, can be detected as either mode switching between modes or polarization change emission. This method enables picosecond resolved observation without disturbances such electronic excitation and heating, it is expected to open doorway observe ultrafast with terahertz pulse.
We investigated the ultrafast terahertz response to photoexcitation for vanadium dioxide single crystals and thin films using optical-pump terahertz-probe technique at room temperature. The optical excitation induced an decrease of transmittance radiation within 0.7ps. Since we expect only free carrier in range, is unambiguously assigned appearance high electronic conductivity due carriers. increases more than ten times picosecond time range after it concluded that states are metallic.
In this paper, few-layer porous graphene is integrated onto the surface of a metasurface layer to provide uniform static electric field efficiently control liquid crystal, thereby enabling flexible metamaterial designs. We demonstrate tunable cross-shaped absorber with different arm lengths driven by combined and electrode. The resulting supports resonant frequency from 0.75 1 THz high-quality factor, amplitude modulation ~80% at these frequencies an applied voltage 10 V. Furthermore,...
Homoepitaxial film and semi-insulating bulk β-Ga2O3 with (001) orientation were studied using terahertz time-domain spectroscopy (THz-TDS) in the frequency region from 0.2 to 3.0 THz parallel [100] [010] directions. The static permittivity of was determined be 10.0 10.4 along a-axis b-axis, respectively, refractive index values at are 3.17 3.23 for each axis. electrical resistivity epilayer extracted good accuracy by employing Drude–Lorentz model without use contacts. This noninvasive...
We report the first observation of sub-terahertz bulk-magnetization precession, using terahertz time-domain spectroscopy. The magnetization precession in gallium-substituted epsilon-iron oxide nano-ferromagnets under zero magnetic field is induced by impulsive THz wave through gyromagnetic effect. Just at resonance frequency, linear to circular polarized conversion realized. This understood as free induction decay signal radiated from a rotating dipole corresponding natural resonance....
The emission with a bandwidth of 1.5 terahertz based on the spin current in ferromagnetic heterostructure Co/Pt is demonstrated. transient launched by NIR femtosecond laser pulse converted into in-plane charge due to inverse Hall effect, which gives rise towards free space. dependence Pt-layer thickness investigated. To optimize geometry structure new type emitter, we developed theoretical model carefully analyzing transport. Our reveals importance take account interfacial loss. It can be...
Recently, <i>p</i>-cresyl sulfate (PCS) has been identified as a protein-bound uremic toxin. Moreover, the serum-free concentration of PCS, which is associated with its efficacy hemodialysis, appears to be good predictor survival in chronic kidney disease (CKD). We previously found that PCS interacts indoxyl (IS), another sulfate-conjugated toxin, during renal excretion via common transporter. The purpose this study was further investigate interaction between and IS on binding human serum...
Tunable liquid crystal devices that can change terahertz wave polarization continuously have many potential applications in optical systems. We present a reflective waveplate with sub-wavelength metal grating and ground plane electrodes. The thickness of the layer be reduced to ~10% needed for same phase shift at given frequency transmissive waveplate. experimentally demonstrate tunability as type just using half thickness. discuss dependence on angle incidence tunability, which achieve beam...
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 ultrafast dynamic magnetooptical effect caused terahertz (THz) irradiation onto chemically synthesized magnetic films based on gallium–titanium–cobalt-substituted ε-Fe2O3 (GTC-ε-Fe2O3) nanoparticles. Visible-light switches sign of Faraday GTC-ε-Fe2O3 films. On other hand, irradiating film...
Gallium nitride (GaN) is one of the most technologically important semiconductors and a fundamental component in many optoelectronic power devices. Low-resistivity GaN wafers are demand actively being developed to improve performance vertical devices necessary for high-voltage high-frequency applications. For development devices, nondestructive characterization electrical properties particularly carrier densities order 1019 cm-3 or higher highly favorable. In this study, we investigated...
In the era of Big Data and Internet Things, data archiving is a key technology. From this viewpoint, magnetic recordings are drawing attention because they guarantee long-term storage. To archive an enormous amount data, further increase recording density necessary. Herein new methodology, "focused-millimeter-wave-assisted (F-MIMR)," proposed. test films based on epsilon iron oxide nanoparticles prepared focused-millimeter-wave generator constructed using terahertz (THz) light. Irradiating...
We compare the ultrafast dynamics of spin reorientation transition in orthoferrite ${\mathrm{Sm}}_{0.7}{\mathrm{Er}}_{0.3}{\mathrm{FeO}}_{3}$ following two different pumping mechanisms. Intense few-cycle pulses midinfrared selectively excite either $f\text{\ensuremath{-}}f$ electronic ${\mathrm{Sm}}^{3+}$ or optical phonons. With phonon pumping, a finite time delay exists for reorientation, reflecting energy transfer between lattice and $4f$ system. In contrast, an instantaneous response is...
Abstract In special relativity, four-vectors, such as space–time, energy–momentum and electromagnetic potential vectors, follow the Lorentz transformation. The transformations of space–time vectors have been tested by time dilation rest mass energy experiments, respectively. However, transformation potentials has never directly demonstrated in experiments due to limitations diagnostics. Here we show spatiotemporal electric-field profiles around a highly energetic electron beam with...
We excite the spin precession in rare-earth orthoferrite YFeO3 by magnetic field of intense terahertz pulse and probe its dynamics transient absorption change near infrared. The observed waveforms contain quasi-ferromagnetic-mode magnon oscillation second harmonics with a comparably strong amplitude. result can be explained dielectric function derived from magnetorefractive Hamiltonian. reveal that harmonic signal microscopically originates novel quasi-ferromagnetic mode at nonlinear regime,...
We introduce a simple and efficient method of enhancing the terahertz field in an air plasma produced by two-color laser pulses, inserting specially designed dual-wavelength wave plate between non-linear optical crystal plasma. Adjusting polarization two pulses yielded electric 1.4 MV/cm, which was 1.7 times as intense that obtained from unmodified system. Additionally, taking dispersion group velocities into account, we discussed validity enhancement factor.
We have generated and detected a longitudinally polarized (Z-polarized) terahertz (THz) wave by focusing conically propagating THz beam from plasma filament induced femtosecond laser pulse. In the experiment, we observed radially field in collimated region Z-polarized at focus time domain. The maximum value of electric reached 1.0 kV/cm. It was also quantitatively discussed about radial focal point. expect this technique to find application domain spectroscopy.