Article
Nanoscience & Nanotechnology
Jiahua Cai, Sai Chen, Chunyan Geng, Jianghao Li, Baogang Quan, Xiaojun Wu
Summary: We investigate the nonlinear modulation dynamics of a THz-nano metasurface on silicon substrates using a time-resolved strong-field THz-pump THz-probe (TPTP) technique. The self-modulation phenomenon with a frequency shift of about 50 GHz is achieved by switching the THz field strength. This phenomenon is attributed to the impact ionization (IMI) of the silicon substrate under the excitation of strong THz fields in nano-gaps.
Article
Chemistry, Physical
Minhaeng Cho
Summary: Coherent multidimensional spectroscopy is widely used for studying the structure and dynamics of chemical and biological systems. It utilizes multiple pulses from mode-locked lasers to control molecular responses for time-resolved measurements. Multiple mode-locked lasers allow for automatic delay time scanning in time-resolved nonlinear spectroscopy by precisely controlling repetition frequencies.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2021)
Article
Chemistry, Physical
Maximilian Spellauge, Jan Winter, Stephan Rapp, Cormac McDonnell, Florian Sotier, Michael Schmidt, Heinz P. Huber
Summary: The ablation rate in double-pulse material processing is significantly affected by the pulse separation, with mechanisms such as rarefaction wave suppression, shielding by ablation plume, and material re-deposition playing important roles. The study found that the rarefaction wave contributes about 25% to the double-pulse ablation volume for aluminum and stainless steel, and about 40% for copper. Ablation efficiency and precision are maximized when energy is coupled into the material before mechanical relaxation or after material surface equilibration.
APPLIED SURFACE SCIENCE
(2021)
Article
Chemistry, Multidisciplinary
K. P. Mithun, Srabani Kar, Abinash Kumar, D. V. S. Muthu, N. Ravishankar, A. K. Sood
Summary: Collective excitation of Dirac plasmons in graphene and topological insulators has led to tunable plasmonic materials. Using OPTP spectroscopy, plasmonic oscillations in bismuth telluride nanowires were demonstrated, showing a Lorentzian response with a resonance frequency shifting with photogenerated carrier density. Modulation depth was found to be tunable by pump fluence, and the time evolution of the system represented a long relaxation channel lasting for more than 50 ps. Model of the decay dynamics highlighted contributions from surface recombination and trap mediated relaxation channels.
Article
Multidisciplinary Sciences
Y. Behovits, A. L. Chekhov, S. Yu. Bodnar, O. Gueckstock, S. Reimers, Y. Lytvynenko, Y. Skourski, M. Wolf, T. S. Seifert, O. Gomonay, M. Klaeui, M. Jourdan, T. Kampfrath
Summary: Antiferromagnets have the potential for ultrafast coherent switching of magnetic order, and can be controlled by electric fields through Neel spin-orbit torques (NSOTs). In this study, we observed field-like terahertz NSOTs in Mn2Au thin films, with a torkance of (150 +/- 50) cm(2) A(-1) s(-1), that can drive a uniform in-plane antiferromagnetic magnon. We also found pronounced nonlinear dynamics and the possibility of fully coherent Neel-vector switching by 90(degrees) within 1 ps.
NATURE COMMUNICATIONS
(2023)
Article
Materials Science, Multidisciplinary
Geunchang Choi, Tuan Khanh Chau, Sung Ju Hong, Dasom Kim, Sung Hyuk Kim, Dai-Sik Kim, Dongseok Suh, Young-Mi Bahk, Mun Seok Jeong
Summary: The study demonstrates a method for achieving negative-type high on/off ratio and ultrafast terahertz modulation using graphene/metal nanoslot antennas. The graphene covering and optical pumping result in resonant modulation of terahertz transmission. Rapid carrier relaxation induced by a strong terahertz field contributes to faster modulation of transient terahertz transmission.
ADVANCED OPTICAL MATERIALS
(2021)
Article
Optics
Marcus Seidel, Federico Pressacco, Oender Akcaalan, Thomas Binhammer, John Darvill, Nagitha Ekanayake, Maik Frede, Uwe Grosse-Wortmann, Michael Heber, Christoph M. Heyl, Dmytro Kutnyakhov, Chen Li, Christian Mohr, Jost Mueller, Oliver Puncken, Harald Redlin, Nora Schirmel, Sebastian Schulz, Angad Swiderski, Hamed Tavakol, Henrik Tuennermann, Caterina Vidoli, Lukas Wenthaus, Nils Wind, Lutz Winkelmann, Bastian Manschwetus, Ingmar Hartl
Summary: The study reports a novel FEL facility laser that combines high average power output and pulse compression for studying ultrafast processes. Compared to other lasers, this new system has improved noise figures, compactness, simplicity, and power efficiency. It provides high-energy, short-duration pulses that can be adjusted through computer control.
LASER & PHOTONICS REVIEWS
(2022)
Article
Chemistry, Multidisciplinary
Petr A. Obraztsov, Vladislava V. Bulgakova, Pavel A. Chizhov, Alexander A. Ushakov, Dmitry S. Gets, Sergey Makarov, Vladimir V. Bukin
Summary: Hybrid organic-inorganic perovskites have shown potential in the development of scalable photoconductive terahertz emitters, with their optoelectronic properties chemically engineerable for desired applications. This study explores the characteristics of polycrystalline perovskite films for THz emission and provides insights into carrier lifetime and mobility using alternative noninvasive methods, showing their competitiveness with traditional semiconductors in THz emission.
Article
Optics
Takeshi Moriyasu, Masahiko Tani, Hideaki Kitahara, Takashi Furuya, Jessica Afalla, Toshiro Kohmoto, Daishiro Koide, Hiroki Sato, Mitsutaka Kumakura
Summary: Optical pump-terahertz probe spectroscopy was used to study the photocarrier dynamics and optical characteristics of semiconductor Si. The results showed that the thickness of Si influenced the transmitted terahertz field amplitude and peak delay time, indicating differences in photocarrier dynamics between different Si materials.
OPTICS COMMUNICATIONS
(2024)
Article
Optics
Gaofang Li, Xiaobo Nie, Yuao Liao, Wen Yin, Wei Zhou, Yanqing Gao, Nenghong Xia, Haoyang Cui
Summary: Ultrafast carrier dynamics and terahertz conductivity of intrinsic 6H-SiC are studied using optical-pump terahertz-probe spectroscopy. The results show that the increase in photogenerated carrier density affects the fast decay time and the evolution of complex conductivity, and the Drude-Smith model provides a better fit for the conductivity.
OPTICS COMMUNICATIONS
(2022)
Article
Nanoscience & Nanotechnology
Zhenyang Xiao, Jiashu Wang, Xinyu Liu, Badih A. Assaf, David Burghoff
Summary: Topological crystalline insulators, which have properties guaranteed by crystalline symmetry, can be tuned in heterostructures and potentially used for terahertz optoelectronic devices. We performed the first optical-pump terahertz-probe spectroscopy to investigate the dynamics of Pb1-xSnxSe at different temperatures. Our experimental observations provide critical information for potential applications of Pb1-xSnxSe and directly measure the topological character of its heterostructures.
Article
Optics
D. Carlson, M. Tanksalvala, D. Morrill, J. San Roman, E. Conejero Jarque, H. C. Kapteyn, M. M. Murnane, M. Hemmer
Summary: This study investigates nonlinear pulse compression at mid-IR wavelengths numerically, revealing a wide range of self-compression possibilities and optimization rules, as well as solitonic dynamics and limitations, setting a framework for future experimental work using few-cycle pulses.
Article
Optics
Ji Chen, Yuan Jin, Liang Gao, John L. Reno, Sushil Kumar
Summary: This study demonstrates wavelength beam-combining of four terahertz distributed-feedback quantum-cascade lasers using low-cost components, achieving collinear propagation and high total power efficiency. The results could pave the way for future commercialization of monolithic terahertz QCL arrays for multi-spectral sensing and spectroscopy at standoff distances.
Article
Nanoscience & Nanotechnology
Aleksander M. Ulatowski, Michael D. Farrar, Henry J. Snaith, Michael B. Johnston, Laura M. Herz
Summary: Tin-iodide perovskites are promising semiconductors for photovoltaic applications due to their higher intrinsic charge-carrier mobilities and lower toxicity. A novel spectroscopic technique was experimentally implemented to investigate the intraband relaxation dynamics of charge carriers in these materials, revealing a push-induced decrease in terahertz conductivity from stimulated THz emission. The study showed that newly photogenerated charge carriers relax quickly on a subpicosecond timescale in the presence of a large population of charge carriers.
Article
Chemistry, Physical
Shaolong Jiang, Jin Yang, Liang Zhu, Jiafeng Xie, Weiteng Guo, Erding Zhao, Chaoyu Chen, Tianwu Wang, Fuhai Su, Yanfeng Zhang, Junhao Lin
Summary: This study successfully fabricated large-sized ultrathin two-dimensional platinum disulfide and investigated its layer-dependent properties. Through analysis of electron energy loss spectroscopy and optical pump-probe spectroscopy, the nonlinearity of the material's response with respect to layer was revealed. This provides important insights into the electronic and optoelectronic properties of two-dimensional platinum disulfide.
Article
Nanoscience & Nanotechnology
Shoji Yoshida, Yusuke Arashida, Hideki Hirori, Takehiro Tachizaki, Atsushi Taninaka, Hiroki Ueno, Osamu Takeuchi, Hidemi Shigekawa
Summary: This study investigated the ultrafast electron dynamics in nanoscale structures, using time-resolved scanning tunneling microscopy/spectroscopy combined with a carrier-envelope phase-controlled subcycle THz electric field. The research successfully visualized electron motion triggered by variation in the lowest unoccupied molecular orbital and distinguished effects of molecular defects with single-molecular-level spatial resolution. This method is expected to play a vital role in evaluating local electronic structures and dynamics for the development of future functional materials and devices.
Article
Physics, Multidisciplinary
Fumiya Sekiguchi, Hideki Hirori, Go Yumoto, Ai Shimazaki, Tomoya Nakamura, Atsushi Wakamiya, Yoshihiko Kanemitsu
Summary: The impact of phonon excitations on the photoexcited carrier dynamics in lead-halide perovskite CH3NH3PbI3 was investigated, showing that strong terahertz excitation can prolong the cooling time of hot carriers. The results demonstrate that phonon excitation significantly perturbs the carrier relaxation dynamics in halide perovskites through the coupling between transverse- and longitudinal-optical phonons.
PHYSICAL REVIEW LETTERS
(2021)
Article
Materials Science, Multidisciplinary
Kotaro Nakagawa, Hideki Hirori, Yasuyuki Sanari, Fumiya Sekiguchi, Ryota Sato, Masaki Saruyama, Toshiharu Teranishi, Yoshihiko Kanemitsu
Summary: Halide perovskite nanocrystals can be tuned for efficient luminescence over a wide wavelength range by changing composition and size. High-order harmonic generation was observed in a CsPbBr3 perovskite nanocrystal film excited by midinfrared laser, with influences from sample structure and nanocrystal orientation on harmonic intensity noted. High-order harmonics from nanocrystal films pave the way for the development of an intensity modulator that can be adjusted by changing excitation ellipticity.
PHYSICAL REVIEW MATERIALS
(2021)
Article
Physics, Applied
Satoshi Kusaba, Kenji Watanabe, Takashi Taniguchi, Kazuhiro Yanagi, Koichiro Tanaka
Summary: In monolayer WSe2, the rise dynamics of out-of-plane polarized photoluminescence from spin-forbidden dark excitons under resonant excitation to bright excitons have been studied, showing a finite rise time and suggesting the importance of intermediate states in the relaxation pathway. Exciton-exciton scattering is found to promote faster relaxation to the spin-forbidden dark excitons.
APPLIED PHYSICS LETTERS
(2021)
Article
Optics
Satoshi Kusaba, Yoshiki Katagiri, Kenji Watanabe, Takashi Taniguchi, Kazuhiro Yanagi, Nobuko Naka, Koichiro Tanaka
Summary: This study demonstrates the properties of dark p-series excitons in monolayer WSe2 using broadband sum frequency generation spectroscopy with a partially incoherent supercontinuum light source. The observed 2p exciton peak energy is higher than predicted due to the Berry phase effect. By measuring excitation intensity and temperature dependence, it was clarified that the broader linewidth of the 2p exciton peak is caused by exciton-electron scattering.
Article
Multidisciplinary Sciences
Go Yumoto, Hideki Hirori, Fumiya Sekiguchi, Ryota Sato, Masaki Saruyama, Toshiharu Teranishi, Yoshihiko Kanemitsu
Summary: By utilizing the multiband structure induced by strong spin-orbit coupling in lead halide perovskites, researchers have demonstrated an anomalous enhancement of exciton energy shift at room temperature. This enhancement at room temperature allows for efficient coherent optical manipulation of excitons utilizing energy states with large spin-orbit splitting, potentially opening up new possibilities for quantum state engineering and ultrafast optical modulation.
NATURE COMMUNICATIONS
(2021)
Article
Nanoscience & Nanotechnology
Takehiro Tachizaki, Kan Hayashi, Yoshihiko Kanemitsu, Hideki Hirori
Summary: The combination of scanning tunneling microscopy and terahertz electromagnetic pulses has advanced significantly, providing atomic-level spatial resolution and femtosecond temporal resolution. It can capture real-time dynamics of electron diffusion and relaxation, and even control molecular motions instantaneously. This technology has great potential for materials research and development in ultrafast time-resolved THz scanning tunneling microscopy.
Article
Nanoscience & Nanotechnology
Ryota Aoki, Kento Uchida, Koichiro Tanaka
Summary: This study investigates a method of inducing topological phase transitions through polarization-controlled infrared excitation and experimentally studies the phenomenon in Td-WTe2 thin films. The experimental results show that polarization-selective excitation leads to the rapid loss of carrier distribution, making it difficult to control the photo-induced phase transition.
Article
Multidisciplinary Sciences
Tomoki Hiraoka, Yuta Inose, Takashi Arikawa, Hiroshi Ito, Koichiro Tanaka
Summary: This paper introduces a resonant-tunneling-diode terahertz oscillator that achieves passive mode-locking and frequency-comb generation through optical feedback. The oscillator, based on a semiconductor device, covers the frequency range of 0.1 to 2 THz. With external bias modulation, the spacing between the comb lines is significantly reduced. A simulation model successfully reproduces the mode-locking behavior. This oscillator can serve as a future frequency standard for terahertz sensing and wireless communications.
NATURE COMMUNICATIONS
(2022)
Article
Optics
F. Blanchard, J. E. Nkeck, L. Guiramand, S. Zibod, K. Dolgaleva, T. Arikawa, K. Tanaka
Summary: This study demonstrates the ability of the surfaces of SrTiO3 crystals at room temperature to act as ultrafast sensors, enabling sub-picosecond switching through the Kerr effect and recording polar THz intensity with spatial resolution below the diffraction limit through THz-field-induced dipole alignment followed by multi-picosecond relaxation time recovery. The contrast sensitivity and spatial resolution achieved by the STO sensor are significantly superior to those of present-day near-field THz sensors based on the linear Pockels effect, providing a new strategy for building an ultrafast space-time THz memory.
Article
Multidisciplinary Sciences
Kento Uchida, Satoshi Kusaba, Kohei Nagai, Tatsuhiko N. Ikeda, Koichiro Tanaka
Summary: In this study, coherent exciton emission in mono-layer WSe2 at room temperature was observed using high-harmonic spectroscopy. The dynamics of Floquet states of excitons were found to be reflected in the coherent exciton emission spectrum. This provides a new approach to Floquet engineering and allows control of quantum materials through pulse shaping of the driving field.
Article
Multidisciplinary Sciences
Zhenya Zhang, Fumiya Sekiguchi, Takahiro Moriyama, Shunsuke C. Furuya, Masahiro Sato, Takuya Satoh, Yu Mukai, Koichiro Tanaka, Takafumi Yamamoto, Hiroshi Kageyama, Yoshihiko Kanemitsu, Hideki Hirori
Summary: The authors studied HoFeO3 crystal using multicycle THz magnetic pulses enhanced strongly by spiral-shaped microstructure. The observed Faraday ellipticity demonstrates second- and third-order harmonics of the magnetization oscillation and an asymmetric oscillation behavior. The ability to drive a spin system to state far from the equilibrium is indispensable for investigating spin structures of antiferromagnets and their functional nonlinearities for spintronics.
NATURE COMMUNICATIONS
(2023)
Article
Physics, Multidisciplinary
Zhenya Zhang, Hideki Hirori, Fumiya Sekiguchi, Ai Shimazaki, Yasuko Iwasaki, Tomoya Nakamura, Atsushi Wakamiya, Yoshihiko Kanemitsu
Summary: Ultrastrong coupling between phonons and vacuum photons was achieved by coupling phonons in perovskite CH3NH3PbI3 films with photons in split ring resonators, reaching the USC regime at a gap size of 100 nm. Nanoresonators were shown to be an excellent platform for studying vacuum-dressed phonon properties.
PHYSICAL REVIEW RESEARCH
(2021)
Article
Materials Science, Multidisciplinary
Shunsuke A. Sato, Hideki Hirori, Yasuyuki Sanari, Yoshihiko Kanemitsu, Angel Rubio
Summary: By using a quantum master equation approach, we investigated high-order harmonic generation (HHG) in graphene and found that the enhancement in HHG originates from an intricate nonlinear coupling between intraband and interband transitions induced by perpendicular electric field components of elliptically polarized light. Additionally, we revealed that contributions from different excitation channels destructively interfere with each other, suggesting a potential pathway to enhance HHG by manipulating band-gap or chemical potential.
Article
Materials Science, Multidisciplinary
Keiichi Ohara, Takumi Yamada, Tomoko Aharen, Hirokazu Tahara, Hideki Hirori, Hidekatsu Suzuura, Yoshihiko Kanemitsu
Summary: Metal halide perovskites have been studied for their versatile photonic device applications, and in this research, the two-photon absorption spectra for CH3NH3PbBr3 perovskite single crystals were reported. The experimental data allowed for the determination of spin-orbit splitting energy and revealed a higher-energy band around 0.8 eV above the band edge, providing insights into the electronic structures and carrier dynamics of halide perovskites.
