The Review of Laser Engineering
Online ISSN : 1349-6603
Print ISSN : 0387-0200
ISSN-L : 0387-0200
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Volume 43, Issue 3
Topical Papers on Frontier of Pulsed Electron Beam for Research on Photoexcited Dynamics
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Topical Papers on Frontier of Pulsed Electron Beam for Research on Photoexcited Dynamics
Topical Paper
Laser Review
  • Preface to Topical Papers on Frontier of Pulsed Electron Beam for Research on Photoexcited Dynamics
    Ryuji ITAKURA
    2015 Volume 43 Issue 3 Pages 136-
    Published: 2015
    Released on J-STAGE: December 17, 2020
    DOIhttps://doi.org/10.2184/lsj.43.3_136
    JOURNAL FREE ACCESS
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  • Evolution of Electron-Microscopes and the Ultrafast Electron Diffraction with Laser Accelerated Electrons
    Shuji SAKABE, Hiroki KURATA, Masaki HASHIDA, Shigeki TOKITA,, Shuns ...
    2015 Volume 43 Issue 3 Pages 138-
    Published: 2015
    Released on J-STAGE: December 17, 2020
    DOIhttps://doi.org/10.2184/lsj.43.3_138
    JOURNAL FREE ACCESS
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    Evolution of advanced electron microscopes is reviewed. Technologies to see not only structure of materials but also information of composition, electronic state, surface structure, and so on have been highly evolved. We are right now on the stage to search their dynamical information. For ultrafast dynamical electron microscopes, ultra-short electron pulse source is crucial. Femtosecond lasers are available to generate short electron pulses. The current state of the research using photocathodes with femtosecond laser is reviewed. The electron pulses generated and accelerated by intense femtosecond lasers are promising for the next-generation sources of intense short pulse electrons. The challenge of the authors at Kyoto University is introduced.
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  • Ultrafast Crystalline-Structural Dynamics by Time-Resolved MeV-Electron Diffraction
    Nobuyasu NARUSE, Yvelin GIRET, Jinfeng YANG, Katsumi TANIMURA
    2015 Volume 43 Issue 3 Pages 144-
    Published: 2015
    Released on J-STAGE: December 17, 2020
    DOIhttps://doi.org/10.2184/lsj.43.3_144
    JOURNAL FREE ACCESS
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    We develop a compact ultrafast electron diffractometer, consisting of a laser-driven rf photocathode that generates 3.0 MeV probe electron pulses with 100-fs temporal widths. High-quality single-shot transmission electron diffraction is detected under kinematic regimes using three-stage lens optics and a high-sensitive detector. Combining theoretical modelling with single-shot diffraction measurements, we are now capable of characterizing the dynamics of atomic structures underpinning the temporal evolution of the Bragg peaks. The feasibility of the approach is demonstrated on the example of photo-induced melting of 10-nm thick gold films. Our results show that dynamic structure determination in laserexcited systems is now a viable prospect using ultrafast electron diffraction.
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  • Femtosecond Time-Resolved Electron Diffraction: Applications for Laser Melting and Ablation
    Masaki HADA
    2015 Volume 43 Issue 3 Pages 149-
    Published: 2015
    Released on J-STAGE: December 17, 2020
    DOIhttps://doi.org/10.2184/lsj.43.3_149
    JOURNAL FREE ACCESS
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    Melting and ablation with an ultrashort laser pulse have been widely used for a variety of applications. The mechanisms of melting and ablation are strongly dependent on the material and photoexcitation levels. Using high peak power laser fluences induces nonthermal processes that involve nonthermal melting, cold ablation and plasma formation; however, thermal related processes are dominant at relatively a low laser fluence. In this paper, we summarize the laser melting and ablation processes from the viewpoint of time-resolved structural studies and introduce the development of a femtosecond timeresolved electron diffraction setup. We also show a time-resolved electron diffraction experiment to study the evolution of the ablation process that follows femtosecond 400-nm laser excitation in crystalline potassium iodide. Our results reveal fast electronic and localized structural changes that lead to the ejection of particles, reflecting the very nature of the strong repulsive forces at play.
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  • Time-Resolved Molecular Orbital Imaging Using Electron Compton Scattering
    Masahiko TAKAHASHI, Masakazu YAMAZAKI
    2015 Volume 43 Issue 3 Pages 154-
    Published: 2015
    Released on J-STAGE: December 17, 2020
    DOIhttps://doi.org/10.2184/lsj.43.3_154
    JOURNAL FREE ACCESS
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    Over the last four decades an experimental method has been developed that looks at molecular orbitals in momentum space. The method, called electron momentum spectroscopy (EMS), is based on electroninduced Compton scattering at incident electron energies of the order of 1 keV or higher. This account reviews the most advanced form of EMS, which is called time-resolved EMS (TR-EMS) and employs ultrashort laser and electron pulses in a pump/probe scheme. To illustrate the current status of TR-EMS, we present an experiment on the three-body photodissociation dynamics of the deuterated acetone molecule at 195 nm. Although there is ample room for improvement such as in data statistics, our experiment demonstrates that molecular orbital imaging of short-lived transient species is feasible, opening the door to exploiting a new area of studies on ultrafast molecular dynamics as well as the nature of molecular excited states.
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  • Femtosecond Laser-Assisted Electron Scattering
    Reika KANYA, Kaoru YAMANOUCHI
    2015 Volume 43 Issue 3 Pages 159-
    Published: 2015
    Released on J-STAGE: December 17, 2020
    DOIhttps://doi.org/10.2184/lsj.43.3_159
    JOURNAL FREE ACCESS
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    We review on recent progress in experimental studies of laser-assisted electron scattering (LAES) induced by femtosecond laser fields. Theoretical backgrounds of the LAES process are briefly surveyed, and earlier experimental studies of LAES processes induced by cw- and pulsed-CO2 laser fields are introduced. Our experimental setup designed for measurements of femtosecond-LAES is described. The recent experimental results of energy spectra and angular distributions of the LAES by Xe atoms are also presented with corresponding results of numerical simulations with and without a light-dressing effect of target atoms. In addition, a novel technique of laser-assisted electron diffraction (LAED) is introduced as an application of the LAES process, and our recent experimental demonstration of the LAED method is presented.
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Laser Original
  • Development of Nanometric Light Spot for Electron-Beam Excitation Assisted Optical Microscope
    Taichi FURUKAWA, Satoshi KANAMORI, Masahiro FUKUTA, Yasunori NAWA, ...
    2015 Volume 43 Issue 3 Pages 164-
    Published: 2015
    Released on J-STAGE: December 17, 2020
    DOIhttps://doi.org/10.2184/lsj.43.3_164
    JOURNAL FREE ACCESS
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    We optimized fabrication condition of ZnO luminescent thin film for electron-beam excitation assisted (EXA) optical microscope. 200 nm gold nanoparticles were observed by EXA microscope using ZnO thin films fabricated at different substrate temperature. ZnO thin films deposited at 400－600℃ can provide a higher signal-to-noise (S/N) ratio than films deposited at 200-300℃. In this research, film deposited at 400℃ was suitable for EXA microscope because the grain size of ZnO film was small and cathodoluminescence intensity was high enough to construct the EXA microscopic image. This ZnO film is a possible candidate for the dynamic observation of living cells with high spatial resolution with EXA microscope.
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