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Temperature Dependence of the Conductivity of InSb Measured by Terahertz Time-Domain Spectroscopy
Shuang Liu;Verdad C. Agulto;Toshiyuki Iwamoto;Kosaku Kato;Valynn Katrine Mag-Usara;Masato Ota;Shamika Dolas;Nathan Newman;Liviu Nedelcu;Masahiko Tani;Masashi Yoshimura;Makoto Nakajima
2023 48th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz)
Year: 2023 | Conference Paper |
In this study, we characterized the temperature-dependent electrical conductivity properties of undoped and lightly doped bulk InSb samples using terahertz time-domain spectroscopy. We obtained the permittivity spectra at low temperatures and analyzed the carrier density and mobility by fitting the spectra to the Drude model. Based on our analysis, we show the temperature dependence of the optical...Show More
Temperature Dependence of the Conductivity of InSb Measured by Terahertz Time-Domain Spectroscopy
Shuang Liu;Verdad C. Agulto;Toshiyuki Iwamoto;Kosaku Kato;Valynn Katrine Mag-Usara;Masato Ota;Shamika Dolas;Nathan Newman;Liviu Nedelcu;Masahiko Tani;Masashi Yoshimura;Makoto Nakajima
Year: 2023 | Conference Paper |
Mapping of Kidney Stone by Far-Infrared Spectroscopy
Verdad C. Agulto;Wangxuan Zhao;Mihoko Maruyama;Masae Takahashi;Kosaku Kato;Valynn Katrine Mag-Usara;Masato Ota;Yutaro Tanaka;Yusuke Mori;Masashi Yoshimura;Makoto Nakajima
2023 48th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz)
Year: 2023 | Conference Paper |
Cited by: Papers (1)
Kidney stones are mainly composed of calcium oxalate (CaOx) minerals, and the understanding of the polymorphisms of CaOx is essential in establishing the pathogenesis of kidney stone formation. CaOx polymorphs are predominantly calcium oxalate monohydrate (COM) and calcium oxalate dihydrate (COD). In this study, we employ reflection-mode Fourier transform infrared spectroscopy in the far-infrared ...Show More
Observation of Anthracene Crystallization under Irradiation of Terahertz Free-Electron Laser
Y.W. Wang;M. Maruyama;M. Ota;K. Kato;V.C. Agulto;V.K. Mag-Usara;H.Y. Yoshikawa;K. Tsukamoto;Y. Tsuri;G. Isoyama;T. Onuma;R. Shimada;T. Tateshima;K. Takano;Y. Tanaka;S. Usami;M. Imanishi;Y. Mori;M. Yoshimura;M. Nakajima
2023 48th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz)
Year: 2023 | Conference Paper |
We explore the potential of using terahertz (THz) free-electron laser (FEL) to induce crystal nucleation in organic materials. We observe the crystallization process of anthracene triggered by irradiating THz-FEL pulses into the supersaturated solution. We found that repeated irradiation with THz-FEL led to the formation of cavitation bubbles near the focal point, which caused many anthracene crys...Show More
Observation of Anthracene Crystallization under Irradiation of Terahertz Free-Electron Laser
Y.W. Wang;M. Maruyama;M. Ota;K. Kato;V.C. Agulto;V.K. Mag-Usara;H.Y. Yoshikawa;K. Tsukamoto;Y. Tsuri;G. Isoyama;T. Onuma;R. Shimada;T. Tateshima;K. Takano;Y. Tanaka;S. Usami;M. Imanishi;Y. Mori;M. Yoshimura;M. Nakajima
Year: 2023 | Conference Paper |
Complex Third Order Nonlinear Optical Susceptibility in the Terahertz Region Evaluated by Free-Electron Laser
Y.W. Wang;T. N. K. Phan;T. Shimizu;M. Ota;K. Kato;K. Kan;V. C. Agulto;V. K. Mag-Usara;G. Isoyama;M. Nakajima
2023 48th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz)
Year: 2023 | Conference Paper |
We experimentally studied the third harmonic generation (THG) from indium arsenide induced by terahertz free-electron laser. The azimuthal angle dependence of THG generation was measured, and we obtained the real and imaginary parts of the susceptibility in the third order. This paves the way for the deeper understanding of nonlinear optics in the high-field region.Show More
Spectral Range Broadening of Multimode-Laser-Driven Terahertz Spectroscopy System Using Two Laser Diodes
Yuanhao Zeng;Valynn Katrine Mag-Usara;Verdad C. Agulto;Kosaku Kato;Masato Ota;Fumiyoshi Kuwashima;Masashi Yoshimura;Makoto Nakajima
2023 48th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz)
Year: 2023 | Conference Paper |
We built a terahertz time-domain spectroscopy system that utilizes two continuous-wave multimode laser diodes with slightly different central wavelengths. We obtained intensified continuous terahertz waves using two multimode laser diodes compared with the case of only one laser diode. The spectral bandwidth of the generated THz wave extended up to 0.5 THz, which was broader than the 0.2 THz bandw...Show More
Observation of Third Harmonic Generation in Two-Dimensional MoS2 Semiconductor Using Terahertz Free-Electron Laser
Youwei Wang;Masato Ota;Verdad C. Agulto;Valynn Katrine Mag-Usara;Mikihiko Nishitani;Goro Isoyama;Makoto Asakawa;Makoto Nakajima
2022 47th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz)
Year: 2022 | Conference Paper |
This study presents the third harmonic generation (THG) in two-dimensional MoS2 deposited on Si/SiO2 substrate. Intense terahertz pulses from a free-electron laser were used as pump. The pump central frequency is 3.5 THz, and the THG peak is observed around 10 THz. The THG intensity dependence on excitation density follows the I_{3 \omega} \propto I_{\omega}^{3} relation which further confirms t...Show More
High Intensity Spintronic Terahertz Emitter with ITO and Microsheet Glass Structure
Taiyo Matsunaga;Valynn Katrine Mag-Usara;Kohei Ejiri;Shoei Tetsukawa;Shuang Liu;Verdad C. Agulto;Shojiro Nishitani;Mikihiko Nishitani;Masashi Yoshimura;Makoto Nakajima
2022 47th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz)
Year: 2022 | Conference Paper |
Cited by: Papers (1)
We demonstrate that an indium tin oxide (ITO) film and microsheet glass layer can be used to increase the intensity of terahertz (THz) radiation from spintronic THz emitters (STEs). In this work, the backward-radiated THz waves of a Pt/Fe bilayer are reflected by an ITO film and subsequently phase-controlled by a microsheet glass to constructively superimpose with forward-radiated THz waves, there...Show More
Structural and electronic origin of spin-dependent interface resistance in spintronic Fe/Pt THz emitter by first-principles calculations
Mary Clare Escaño;Tien Quang Nguyen;Valynn Katrine Mag-Usara;Miezel Talara;Masahiko Tani
2022 47th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz)
Year: 2022 | Conference Paper |
Using first-principles methods based on spin density functional theory (SDFT) and multichannel Landauer formalism for spin-transport, we calculated the spin-dependent interface resistance arising from the interface potential barrier due to the shifts in minority (spin-up) and majority (spin-down) conduction bands between Fe and Pt in spintronic Fe/Pt THz emitter. We found that the spin-up interfac...Show More
Experimental Study of Electron Impact Ionization between a Relativistic Electron Bunch and a ZnTe Crystal
M. Ota;K. Kan;S. Komada;Y. Wang;V. C. Agulto;V. K. Mag-Usara;Y. Arikawa;T. Matsui;Y. Sakawa;M. Nakajima
2022 47th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz)
Year: 2022 | Conference Paper |
We utilized electro-optic (EO) sampling to measure the electric field induced by a 35-MeV picosecond electron bunch propagating inside a ZnTe crystal. We injected electron bunches into the crystal and probed the irradiation effect. We found that the electron bunch positively charges up the crystal via impact ionizations through the collision between the fast electrons and bounded electrons inside ...Show More
Generation of Circularly Polarized Continuous Terahertz Waves Using 650-nm Chaotic Multimode Semiconductor Laser
Valynn Katrine Mag-Usara;Jiajun Li;Verdad C. Agulto;Izumi Ohta;Fumiyoshi Kuwashima;Masashi Yoshimura;Makoto Nakajima
2022 47th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz)
Year: 2022 | Conference Paper |
We developed a terahertz time-domain spectroscopy (THz-TDS) system with a chaotic continuous wave (CW) light source based on a 650-nm multimode laser diode. We consequently demonstrated that the photoexcitation of a spiral photoconductive antenna by the 650-nm chaotic laser generates CW THz radiation with comb-like sub-THz frequency spectrum, which has very narrow-spaced modes at 0.025-THz interva...Show More
Laser-Induced Periodic Surface Structures on Ge2Sb2Te5 Irradiated by Terahertz Free-Electron Laser Vortex Beam
Youwei Wang;Sadashi Segawa;Tomoki Shimizu;Masato Ota;Verdad C. Agulto;Valynn Katrine Mag-Usara;Katsuhiko Miyamoto;Takashige Omatsu;Kotaro Makino;Junji Tominaga;Goro Isoyama;Makoto Asakawa;Makoto Nakajima
2022 47th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz)
Year: 2022 | Conference Paper |
Cited by: Papers (1)
Laser-induced ablation of Ge2Sb2Te2 using terahertz vortex beam was investigated. Intense terahertz pulses from a free-electron laser were made to pass through a Tsurupica spiral phase plate to generate the vortex beam. Laser-induced periodic surface structures (LIPSS) were formed with a period quarter of the wavelength and an orientation parallel to the beam polarization. Due to the singularity o...Show More
Laser-Induced Periodic Surface Structures on Ge2Sb2Te5 Irradiated by Terahertz Free-Electron Laser Vortex Beam
Youwei Wang;Sadashi Segawa;Tomoki Shimizu;Masato Ota;Verdad C. Agulto;Valynn Katrine Mag-Usara;Katsuhiko Miyamoto;Takashige Omatsu;Kotaro Makino;Junji Tominaga;Goro Isoyama;Makoto Asakawa;Makoto Nakajima
Year: 2022 | Conference Paper |
Single-Shot Measurement of Relativistic Electron Bunch Using Electro-Optic Sampling
K. Kan;M. Ota;S. Komada;Y. W. Wang;V. C. Agulto;V. K. Mag-Usara;Y. Arikawa;T. Matsui;Y. Sakawa;M. Nakajima
2022 47th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz)
Year: 2022 | Conference Paper |
Single-shot measurement of radiations such as electron beams, ion beams, neutrons, and X-rays, helps diagnose the quality of beams and improve practical applications. This paper presents a single-shot measurement of relativistic electron bunch using electro-optic (EO) sampling. To realize single-shot measurement, the spatio-temporal distribution of a femtosecond laser was manipulated by an optical...Show More
Terahertz Time-Domain Ellipsometry of Heavily Doped β-Ga2 O3
Verdad C. Agulto;Toshiyuki Iwamoto;Youwei Wang;Shuang Liu;Valynn Katrine Mag-Usara;Ken Goto;Hisashi Murakami;Yoshinao Kumagai;Makoto Nakajima
2022 47th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz)
Year: 2022 | Conference Paper |
Heavily doped \beta-Ga_{2} O_{3} single crystal was investigated using terahertz time-domain ellipsometry. \beta-Ga_{2} O_{3} is anisotropic, hence, measurements were performed at different sample azimuthal angles. The optical properties were found to be largely influenced by the free carriers than the anisotropic background permittivity, and phonon effects were negligible in the measureme...Show More
Absorption Properties of Calcium Oxalate in the Far-Infrared Region for Phase Identification in Kidney Stones
Verdad C. Agulto;Shintaro Sakamoto;Mihoko Maruyama;Valynn Katrine Mag-Usara;Yusuke Mori;Masashi Yoshimura;Makoto Nakajima
2022 47th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz)
Year: 2022 | Conference Paper |
Cited by: Papers (2)
Calcium oxalate is the main constituent of kidney stones, and it exists either in monohydrate or dihydrate form. Herein calcium oxalate dihydrate was investigated by Fourier transform infrared (FTIR) spectroscopy in the far-infrared region. The results reveal a characteristic absorption band around 8.5 THz. This finding could be useful in the phase identification of kidney stones which is valuable...Show More
THz Spectroscopy of the Anisotropic Refractive Index of β-Ga2O3
V.C. Agulto;K. Toya;T.N.K. Phan;V.K. Mag-Usara;J. Li;M.J.F. Empizo;T. Iwamoto;K. Goto;H. Murakami;Y. Kumagai;N. Sarukura;M. Yoshimura;M. Nakajima
2021 46th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz)
Year: 2021 | Conference Paper |
We investigated the monoclinic β-Ga2O3 ultrawide-bandgap semiconductor using transmission terahertz time-domain spectroscopy (THz-TDS). To characterize the anisotropic properties, the complex refractive index of a semi-insulating bulk and of an n-type Si-doped homoepitaxial film were obtained along the [100] and [010] directions. The material response can be well-described by the Drude-Lorentz mod...Show More
Spectroscopic Ellipsometry of InSb in the Terahertz Region
Verdad C. Agulto;Toshiyuki Iwamoto;Kazuhiro Toya;Valynn Katrine Mag-Usara;Shamika Dolas;Nathan Newman;Liviu Nedelcu;Masahiko Tani;Makoto Nakajima
2021 46th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz)
Year: 2021 | Conference Paper |
Cited by: Papers (1)
Herein we show the terahertz (THz) time-domain ellipsometry investigation of the InSb semiconductor. At room temperature, the carriers of InSb are thermally excited to the conduction band due to its narrow bandgap. We, nevertheless, show that THz ellipsometry can detect subtle differences between carrier densities of undoped and lightly doped InSb bulk semiconductors. The advantage of THz ellipsom...Show More
Measurement of the Azimuthal Angle Dependence of Third Harmonic Generation from Narrow-gap Semiconductor Surfaces
Y.W. Wang;T. Shimizu;T. N. K. Phan;K. Kan;V.C. Agulto;V.K. Mag-Usara;G. Isoyama;M. Nakajima
2021 46th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz)
Year: 2021 | Conference Paper |
Reflection type measurements were performed on narrow-gap semiconductors such as InSb and InAs bulk samples for harmonic generation using intense terahertz pulses from free electron laser. We successfully measured the characteristic azimuthal angle dependence of the third harmonic generation (THG). The results show cos3θ and cos6θ dependence at different polarization layouts for InAs(111).Show More
Study of the spatio-temporal profile diagnostics for relativistic picosecond electron bunches by electro-optic sampling
M. Ota;K. Kan;S. Komada;Y. Arikawa;V. K. Mag-Usara;V. C. Agulto;Y.W. Wang;Y. Sakawa;T. Matsui;M. Nakajima
2021 46th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz)
Year: 2021 | Conference Paper |
Electric field profiles around a relativistic electron bunch along the propagation and in the radial direction are measured by the electro-optic (EO) sampling. The longitudinal (temporal) profile is obtained by changing the arrival time on the EO crystal between the electron bunch and the pulsed probe laser, while the transverse (radial) profile is investigated by lateral shift of the electron bea...Show More
Study of Generation and Detection of Continuous Terahertz Wave Using Chaotic Multi-mode Semiconductor Laser
Jiajun Li;Valynn Katrine Mag-Usara;Verdad C. Agulto;Izumi Ohta;Fumiyoshi Kuwashima;Masashi Yoshimura;Makoto Nakajima
2021 46th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz)
Year: 2021 | Conference Paper |
A 650-nm chaotically oscillating multi-mode semiconductor laser was used to generate and detect a stable continuous terahertz signal from a photoconductive antenna. The intensity of the generated terahertz was ~10 times stronger compared to the excitation without chaotic oscillations. The frequency comb-type spectrum is obtained in the sub-terahertz region, which makes terahertz time-domain spectr...Show More
Initiation of THz Spherical Wave of Electron Bunch near Metallic Boundary
K. Kan;M. Ota;S. Komada;Y. Arikawa;V. K. Mag-Usara;V. C. Agulto;Y. W. Wang;Y. Sakawa;T. Matsui;M. Nakajima
2021 46th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz)
Year: 2021 | Conference Paper |
Cited by: Papers (1)
Spatio-temporal measurement of THz spherical wave generated by the electron bunch passing across a metallic foil was conducted. Transverse THz electric field around a relativistic sub-picosecond electron bunch was measured using electro-optic (EO) sampling based on balance detection. The shape of the spherical wavefront was changed by adjusting the longitudinal position of the metallic foil which ...Show More
Lorentz contraction of an electric field around relativistic electron beams
M. Ota;K. Kan;Y. Arikawa;V. K. Mag-Usara;V. C. Agulto;Y.W. Wang;S. Komada;Y. Sakawa;T. Matsui;M. Nakajima
2021 46th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz)
Year: 2021 | Conference Paper |
Spatio-temporal terahertz electric field profiles around 35 MeV electron bunches propagating in the air are measured by the echelon-based single-shot electro-optic measurement with a sub-picosecond temporal resolution. We demonstrates that the Lorentz contraction of the electric field in the direction perpendicular to the pass of the electron beams is directly observed.Show More
Transmittance Properties of Metallic Double-Coil Array as Terahertz Absorber
Z. Ling;V.K. Mag-Usara;V.C. Agulto;M. Haga;M. Yoshimura;M. Nakajima
2021 46th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz)
Year: 2021 | Conference Paper |
Cited by: Papers (1)
An array of tungsten double coils embedded in polyester resin was investigated as an electromagnetic wave absorber. The finite element method was used to numerically find the best structure of the coils. Then, the transmittance response of the sample was evaluated experimentally using terahertz time-domain spectroscopy. Results show that such double-coil array is an effective electromagnetic wave ...Show More
Spintronic Terahertz Emission and Magnetic Anisotropy of Epitaxial Platinum Heterostructures on MgO(110) Substrate
Shoei Tetsukawa;Shuang Liu;Valynn Katrine Mag-Usara;Verdad Canila Agulto;Makoto Kohda;Ryan Thompson;Hiromu Gamou;Ye Du;Shutaro Karube;Junsaku Nitta;Masahiko Tani;Makoto Asakawa;Makoto Nakajima
2021 46th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz)
Year: 2021 | Conference Paper |
Spintronic terahertz emitters are terahertz wave emitting elements that utilize spin currents. We have produced Pt/Co spintronic terahertz emitters by epitaxial growth of Pt and Co layers on MgO(110) substrate. The azimuthal angle dependence of Pt/Co spintronic terahertz emission shows characteristic dependences due to magnetic anisotropy. The terahertz emission is useful to evaluate the magnetic ...Show More
Spintronic Terahertz Emission and Magnetic Anisotropy of Epitaxial Platinum Heterostructures on MgO(110) Substrate
Shoei Tetsukawa;Shuang Liu;Valynn Katrine Mag-Usara;Verdad Canila Agulto;Makoto Kohda;Ryan Thompson;Hiromu Gamou;Ye Du;Shutaro Karube;Junsaku Nitta;Masahiko Tani;Makoto Asakawa;Makoto Nakajima
Year: 2021 | Conference Paper |
Pt/Fe on Plano-convex Glass Substrate as a Terahertz Emitter with Built-in Focusing Lens for Spintronic Terahertz Radiation
Valynn Katrine Mag-usara;Shoei Tetsukawa;Shuang Liu;Verdad C. Agulto;Mikihiko Nishitani;Masahiko Tani;Makoto Nakajima
2021 46th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz)
Year: 2021 | Conference Paper |
A spintronic heterostructure consisting of Pt and Fe thin films deposited by magnetron sputtering on a convex glass lens is demonstrated as a terahertz emitter. The experimental results show that the convex type spintronic terahertz emitter focuses its radiated terahertz beam without the need for any additional optics, thereby allowing opportunities for the simplification of terahertz setups.Show More
Terahertz Emission Properties from Fe/Pt Metallic Spintronic Hetero-Structures
M. Tani;V. Mag-usara;M. Talara;C. Tachioka;J. Afalla;J. Muldera;T. Furuya;M. C. S. Escaño;G. Torosyan;L. Scheuer;D. Sokoluk;M. Rahm;E. Th. Papaioannou;R. Beigang;C. E. Petoukhoff;J. Madéo;K. M. Dani;K. Saito;Q. Guo;H. Kitahara;M. Nakajima;D. Bulgarevich;M. Watanabe
2020 IEEE International Conference on Plasma Science (ICOPS)
Year: 2020 | Conference Paper |
Spintronic terahertz (THz) emitters [1]–[2], consisting of ultrathin ferromagnetic and non-ferromagnetic metallic layers, have advantages over conventional THz emitters, such as photoconductive antennas (PCAs). For example, the emission bandwidth is much broader than a typical PCA [2]. A broad range of optical pump wavelength from UV to near IR region, including the communication wavelength $(\sim...Show More
Terahertz Emission Properties from Fe/Pt Metallic Spintronic Hetero-Structures
M. Tani;V. Mag-usara;M. Talara;C. Tachioka;J. Afalla;J. Muldera;T. Furuya;M. C. S. Escaño;G. Torosyan;L. Scheuer;D. Sokoluk;M. Rahm;E. Th. Papaioannou;R. Beigang;C. E. Petoukhoff;J. Madéo;K. M. Dani;K. Saito;Q. Guo;H. Kitahara;M. Nakajima;D. Bulgarevich;M. Watanabe
Year: 2020 | Conference Paper |
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