A5063880581- Particle Accelerators and Free-Electron Lasers
- Gyrotron and Vacuum Electronics Research
- Advanced X-ray Imaging Techniques
- Laser Design and Applications
- Particle accelerators and beam dynamics
- Laser-Plasma Interactions and Diagnostics
- Laser-Matter Interactions and Applications
- Terahertz technology and applications
- Atomic and Subatomic Physics Research
- Photocathodes and Microchannel Plates
- Laser Material Processing Techniques
- Crystallography and Radiation Phenomena
- Radiation Detection and Scintillator Technologies
- Advanced Fiber Laser Technologies
- Solid State Laser Technologies
- Advanced Radiotherapy Techniques
- Atomic and Molecular Physics
- Advancements in Photolithography Techniques
- X-ray Spectroscopy and Fluorescence Analysis
- Laser-induced spectroscopy and plasma
- Integrated Circuits and Semiconductor Failure Analysis
- Advanced Surface Polishing Techniques
- Orbital Angular Momentum in Optics
- Advanced X-ray and CT Imaging
- Superconducting Materials and Applications
The University of Tokyo
2018-2024
Waseda University
2014-2023
Japan Research Institute
2012
High Energy Accelerator Research Organization
2007
Nagasaki University
1976
Kagoshima University
1976
We demonstrated spectral control of beyond extreme ultraviolet (B-EUV) emission at a central wavelength 6.76 nm from gadolinium (Gd) laser-produced plasma. The highest purity (SP) was 5.1% under dual 1-μm laser pulse irradiation. It doubled compared to value 2.4% attained single irradiation solid density Gd because the reduction in optical depth. maximum SP higher than that obtained using mid-infrared 10.6 μm. for 150-ps main also 6-ns Our approach can be extended solid-state plasmas (LPPs)...
We have demonstrated for the first time production of highly polarized short-pulse positrons with a finite energy spread in accordance new scheme that consists two-quantum processes, such as inverse Compton scattering and electron-positron pair creation. Using circularly laser beam 532 nm scattered off high-quality, 1.28 GeV electron beam, we obtained an intensity 2 x 10(4) e+ /bunch. The magnitude positron polarization has been determined to be 73 +/- 15(stat) 19(syst)% by means newly...
Abstract Interaction of a solid material with focused, intense pulses high-energy photons or other particles (such as electrons and ions) creates strong electronic excitation state within an ultra-short time on ultra-small spatial scales. This offers the possibility to control response scale less than nanometer—crucial for next generation nano-devices. Here we create craters surface silicon substrate by focusing single femtosecond extreme ultraviolet pulse from SACLA free-electron laser. We...
We have demonstrated angular distribution separation of the extreme ultraviolet (EUV) emission and suprathermal ions with a significant energy reduction for produced using dual pulse irradiation planar gadolinium (Gd) target. The time between pre-pulse main laser heating was set at 30 ns, pre-plasma irradiated distance 50 μm above Angular distributions EUV were almost isotropic followed cos4θ distribution, respectively. emitted normal to target along axis. most probable less than 2 keV,...
We demonstrated an efficient extreme ultraviolet (EUV) source at a wavelength of 13.5 nm using spatially separated multiple solid-state-laser pulse irradiation. The maximum conversion efficiency (CE) achieved was 3.8% for ±30° oblique laser injection, which about twice as high that single irradiation 1.7%, with EUV size 100 μm two pulses total energy 500 mJ intensity 2×1011 W/cm2. In addition, we CE 4.7% ±60° one the highest values ever reported, in case 1-μm solid-state laser-produced...
X-ray generation based on laser-electron Compton scattering is one attractive method to achieve a compact laboratory-sized high-brightness x-ray source. We have designed, built, and tested such source; it combines 50 MeV multibunch electron linac with mode-locked 1064 nm laser stored amplified in Fabry–Pérot optical cavity. directly observed trains of pulsed x rays using microchannel plate detector; the resultant yield was found be 1.2×105 Hz good agreement prediction. believe that result...
Vectorial vortex analysis is used to determine the polarization states of an arbitrarily polarized terahertz (0.1-1.6 THz) beam using THz achromatic axially symmetric wave (TAS) plates, which have a phase retardance Δ = 163° and are made polytetrafluorethylene. Polarized beams converted into vectorial with no spatial or wavelength dispersion, unknown incident reconstructed. The determination also demonstrated at frequencies 0.16 0.36 THz. results obtained by solving inverse source problem...
A free-electron laser (FEL) is a robust tool for studying the interaction of intense X-rays with matter. In this study, we investigate damage threshold and morphology fused silica irradiated by extreme ultraviolet femtosecond pulses FEL. The experimental results indicate superiority FEL processing. FEL-damage at wavelength 13.5 nm 0.17 J/cm2, which 20 times lower than that near infrared (NIR) laser. relationship between crater depth fluence reveals effective absorption length αeff−1 = 58 nm....
We describe the production of mid-infrared (mid-IR) short carbon dioxide (CO2) laser pulses with variable durations from 3 to 15 ns at a maximum pulse energy 150 mJ/pulse using germanium (Ge) substrate semiconductor switch and multipass amplifier. The results clearly show spectral profiles possess all desired characteristics as well possibility obtaining an conversion efficiency close theoretical upper limit. It is also shown that it necessary irradiate less than 10 optimize efficient EUV...
At the laser undulator compact x-ray source at KEK, our group has designed and built a new rf gun with larger mode separation of 8.6 MHz higher $Q$ value than earlier guns. This paper presents details on design fabrication, low-power measurements, tuning procedures followed in fabrication cavity. We also give detailed account experiments performed this present measurement results. have successfully generated 100 bunches per train 50 nC charge 41 MeV 300 160 5 MeV, low peak-to-peak energy...
We demonstrate the creation of a vector beam by tailoring geometric phase left- and right- circularly polarized beams. Such with uniform has not been demonstrated before because vortex remains in beam. focus on cancellation to generate beams terahertz regions, measure its spatial distribution polarization. conduct proof-of-principle experiments for producing radial polarization at 0.36 THz. determine be below 4%, thus highlighting extendibility availability proposed concept super broadband...
We report the spectral behavior and averaged output power of a supercontinuum beam generated with an ytterbium (Yb)-doped double-clad passive fiber as gain media for amplifier mode-locked oscillator at repetition rate 10 MHz. The flat spectra was observed wavelength average 6.2 W in near-infrared range 1–2.3 μm, which represents bandwidth 1.1 μm 20-m-long Yb-doped fiber.
We demonstrate sub-micrometer processing of two kinds thin films, polymethyl methacrylate (PMMA) and metal nano-particle resist, by focusing high-order harmonics near-IR femtosecond laser pulses in the extreme ultraviolet (XUV) wavelength region (27.2-34.3 nm) on film samples using an ellipsoidal mirror. The ablation threshold fluences for PMMA sample resist per XUV pulse obtained accumulation 200 were determined to be 0.42mJ/cm2 0.17mJ/cm2, respectively. diameters (FWHM) a hole created at...
The many tunable parameters involved in laser processing, such as wavelength, pulse duration, energy, and scan speed, not to mention various other complicating factors on the material side, makes it practically impossible reliably find an optimized parameter set realize a specific processing target. Currently, acceptable is mainly found by tapping experience intuition of skilled people within present production system. However, methods do scale mass-customization needs coming super-smart...
We present a new design for rf electron gun to be used in ultrashort ($\ensuremath{\sim}1\text{ }\text{ }\mathrm{ps}$) bunch generation. Using both simulation and measurement we evaluated the principle of this type were able confirm an During simulation, length less than 100 fs(rms) with $100\text{ }\mathrm{pC}/\text{bunch}$ charge was confirmed at optimum operating condition. The is produce linearly distributed longitudinal phase space by using attached output cell specially designed energy...
We propose and demonstrate production of a supercontinuum vector beam by independent manipulations an angular polarization geometric phase. The proposed concept consists left- right-hand vortex phase cancelation. Two-dimensional distributions the in generated are evaluated for rigorous analysis. Their azimuthal angles linearly changed with matching ratios more than 90%, as compared to theoretical calculations. obtained from ellipsometric parameters is also shaped be uniform at average 0.10...