A5021193165- Diamond and Carbon-based Materials Research
- Laser-Matter Interactions and Applications
- Electronic and Structural Properties of Oxides
- Spectroscopy Techniques in Biomedical and Chemical Research
- Advanced Chemical Physics Studies
- Spectroscopy and Chemometric Analyses
- Iron-based superconductors research
- Spectroscopy and Laser Applications
- Photocathodes and Microchannel Plates
- Cold Atom Physics and Bose-Einstein Condensates
- High-pressure geophysics and materials
- Semiconductor Lasers and Optical Devices
- Photochromic and Fluorescence Chemistry
- Advanced Fluorescence Microscopy Techniques
- Rare-earth and actinide compounds
- Photochemistry and Electron Transfer Studies
- Electron and X-Ray Spectroscopy Techniques
- Advanced Fiber Laser Technologies
- Laser Design and Applications
- Photoreceptor and optogenetics research
- Photorefractive and Nonlinear Optics
- Advanced Optical Sensing Technologies
- Photonic and Optical Devices
- Atomic and Subatomic Physics Research
- Advanced X-ray Imaging Techniques
The University of Tokyo
2009-2022
Japan Science and Technology Agency
2013-2022
Kwansei Gakuin University
2020
We study superconducting FeSe $({T}_{\mathrm{c}}\phantom{\rule{0.16em}{0ex}}=\phantom{\rule{0.16em}{0ex}}9\phantom{\rule{0.16em}{0ex}}\mathrm{K})$ exhibiting the tetragonal-orthorhombic structural transition $({T}_{\mathrm{s}}\phantom{\rule{0.16em}{0ex}}\ensuremath{\sim}\phantom{\rule{0.16em}{0ex}}90\phantom{\rule{0.16em}{0ex}}\mathrm{K})$ without any antiferromagnetic ordering, by utilizing angle-resolved photoemission spectroscopy. In detwinned orthorhombic state, energy position of...
We investigate the electronic reconstruction across tetragonal-orthorhombic structural transition in FeSe by employing polarization-dependent angle-resolved photoemission spectroscopy (ARPES) on detwinned single crystals. Across transition, structures around G and M points are modified from four-fold to two-fold symmetry due lifting of degeneracy dxz/dyz orbitals. The dxz band shifts upward at point while it moves downward point, suggesting that structure orthorhombic is characterized a...
We combine sub-20 fs transient absorption spectroscopy with state-of-the-art computations to study the ultrafast photoinduced dynamics of trans-azobenzene (AB). are able resolve lifetime ππ* state, whose decay within ca. 50 is correlated buildup nπ* population and emergence coherences in dynamics, date unobserved. Nonlinear simulations call for CNN in-plane bendings as active modes subps coherent out state. Radiative kinetic energy transfer into these drives system a high-energy planar...
We demonstrate ultra-broadband Fourier-transform coherent anti-Stokes Raman scattering (FT-CARS) spectroscopy spanning over 3,000 cm-1 with a rapid-scan Michelson interferometer at scan rate of 24,000 spectra/s. Using sub-10-fs optical pulses from mode-locked laser, we measure broad CARS spectrum covering both the fingerprint region (500-1,800 cm-1) and C-H, N-H, O-H stretching (2,700-3,600 cm-1). To best our knowledge, this is first demonstration more than 10,000 Our system holds potential...
We have found a series of resonances associated with the bound state (polyexcitons, PE(N)s) N excitons up to N=6 in emission spectra diamond under two-photon excitation at around 10 K. Time-resolved show stepwise formation PE(N)s smaller larger N, as well successive decay from N. At higher levels, transformation into condensed phase electron-hole droplets occurs. The binding energies PE(N)s, normalized exciton Rydberg energy, agree those silicon, suggesting universality phenomena.
We report on the observation of periodic modulations in second-order photon correlation single-mode vertical-cavity surface-emitting lasers (VCSELs) steady-state operations. realized fast measurement VCSELs by using a streak camera operated photon-counting mode. Fast modulation signals were observed correlations at and around threshold.The calculations rate equations that include gain medium dynamics shows oscillating originate from relaxation oscillations.
We have measured transients of excitonic luminescence under pulsed excitation single-crystal diamond, synthesized by a high-temperature high-pressure method. The longest decay time 80 ns is at lattice temperature around 100 K in nondoped samples. kinetics strongly depends on the power density and impurity concentration. Based concentrations determined from infrared ultraviolet absorption coefficients, we simulate carrier solving rate equations for free bound exciton densities. It found that...
Abstract We have observed edge emission due to free excitons and electron–hole droplets in diamond by two‐photon excitation using subpicosecond laser pulses at 257 nm. find that excitonic temperatures under are much lower than the case of one‐photon excitation. A minimum temperature 3.4 K is extracted spectral analysis. In order understand difference excitations, we discuss a heating mechanism which depends on density distribution pairs crystal along beam. (© 2008 WILEY‐VCH Verlag GmbH &...
We present time-integrated and time-resolved photoluminescence spectra of excitons electron-hole droplets in externally stressed diamond. A suppression droplet luminescence an enhancement exciton are clearly observed due to the application strain field, reducing degeneracy conduction bands. observe that a $1.1\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ stress crystal results decrease critical temperature by approximately $10\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. Based on these results, we...
Nonlinear optical microscopy allows for rapid high-resolution with image contrast generated from the intrinsic properties of sample. Established modalities, such as multiphoton excited fluorescence and second/third-harmonic generation, can be combined other nonlinear techniques, coherent Raman spectroscopy, which typically allow chemical imaging a single resonant vibrational mode Here, we utilize ultrafast laser source to obtain broadband spectra on microscope, together approaches same...
We demonstrate a scheme for efficient generation of 5.9 eV coherent light source with an average power 23 mW, 0.34 meV linewidth, and 73 MHz repetition rate from Ti: sapphire picosecond mode-locked laser output 1 W. Second-harmonic is generated in passive optical cavity by BiB(3)O(6) crystal conversion efficiency as high 67%. By focusing the second-harmonic transmitted into β-BaB(2)O(4) crystal, we obtain fourth-harmonic at eV. This offers stable operation least week. discuss suitability...
Exploring the properties of a highly quantum-degenerate electron-hole (e-h) state as many-body system is an interesting problem in solid-state physics. Electron-hole droplets (EHDs) offer potential platform for investigating such Fermi-degenerate carriers at extremely high density. Herein we present dielectric response measurements mid-infrared (MIR) region definitive evaluation dynamic e-h EHDs diamond. With photoexcitation across band-gap energy by using two-photon absorption process,...
We demonstrate a formation control of electron-hole droplets (EHD) in diamond by weak pulse injection. At high temperatures, we find large enhancement the luminescence signal from EHD. On other hand, decreases when lower temperature, indicating decrease droplet size and instability In this region, ensembles might form new phase consisting multi-excitonic clusters.
We report a broadband refractive index measurement method based on higher harmonic generation tabletop coherent extreme ultraviolet source. measured the complex of sample material by measuring interference pattern produced bare double slit and comparing this with another one covered material. validated aluminum in photon energy range 63–78 eV using neon gas jet. The system had errors less than 0.02%.
Frequency recognition algorithm for multiple exposures (FRAME) is a high-speed videography technique that exposes dynamic object to time-varying structured illumination (SI) and captures two-dimensional transients in single shot. Conventional FRAME requires light splitting increase the number of frames per shot, thereby resulting optical loss limited Here, we propose demonstrate novel method which overcomes these problems by utilizing an interferometer generate SI without splitting....
Summary form only given. Angle-resolved photoelectron spectroscopy (ARPES) is a powerful tool to provide direct information on the electronic structures of materials in energy-momentum space. Recent instrumental developments offer us an opportunity explore fine near Fermi surface [1, 2]. To use capability high-resolution ARPES, we should develop vacuum ultraviolet (VUV) light sources with sub-meV linewidths. However, using typical synchrotron radiation and gas discharge lamps, it takes much...