15:00-, MON, 18-OCT-2021
The 83rd KPSI Seminar, QST
A119, KPSI-QST and Web

Building Science and Theory of Laser-Matter Interaction
toward Super-Smart Society
Kenichi L. Ishikawa

Department of Nuclear Engineering and Management, Graduate School of Engineering,
The University of Tokyo, Japan
Photon Science Center, Graduate School of Engineering, The University of Tokyo, Japan
Research Institute for Photon Science and Laser Technology, The University of Tokyo, JapanThe Physics Nobel Prize in 2018 was awarded for groundbreaking inventions in the field of laser physics to A.
Ashkin, G. Mourou, and D. Strickland. The prize motivation for the latter two was “for their method ofgenerating high-intensity, ultra-short optical pulses,” i.e., chirped-pulse amplification (CPA). The Nobel
Committee for Physics names CPA technology's major applications, among which the first is strong-field
physics and attosecond science and the third high-intensity lasers in industry and medicine.
Strong-field physics and attosecond science are rapidly progressing toward a world-changing goal of
direct measurement and, ultimately, control of the electron motion in matters. To exactly simulate intenselaser-driven multielectron dynamics in atoms and molecules from the first principles (ab initio strong-fieldphysics), we have developed various cost-effective wavefunction-based methods such as time-dependent
multiconfiguration self-consistent-field (TD-MCSCF) methods [1], the time-dependent optimized coupledcluster (TD-OCC) methods using time-varying orbitals, and the gauge-invariant time-dependentconfiguration-interaction-singles (TDCIS) method. In this talk, we report their formulations, numerical
implementations, and comparison with experimental results.
Thanks to the advent of high-intensity mid-infrared to terahertz radiation sources, solid-state materials
have recently emerged as a new stage of strong-field physics and attosecond science. In particular, themechanism of high-harmonic generation (HHG) from solids are under intensive discussion. Here wetheoretically discuss the momentum-space pictures of HHG from crystalline dielectrics and semiconductors[2]. We introduce a multiband momentum-space three-step model that incorporates intraband displacement,interband tunneling, and recombination with a valence-band hole. We also analyze how the model is modified
by electron-hole interaction. Then, we present a time-dependent density-matrix method that simulates HHG
from actual three-dimensional materials.
The extension of the frontier of strong-field physics and attosecond science from atomic and molecularsystems to solid-state materials will further advance application of high-intensity lasers in industry andmedicine, such as laser processing. Laser processing is flexible with many parameters such as wavelength,
pulse duration, and pulse energy. Today, these parameters are optimized by human experience and intuition.
To meet the mass customization need in the coming super smart society, it is time to replace them withapproaches driven by data, artificial intelligence (AI), and science & theory that highly integrate cyberspaceand physical space (CPS) [3]. To promote smart production, we develop CPS laser manufacturing capable ofproposing the optimal processing parameters based on simulation in cyberspace. Understanding laser
processing belongs to multiscale and multidisciplinary cutting-edge science, involving highly nonlinear,dynamical processes. One of our focuses is to understand and simulate such strong laser matter interaction by
combining different techniques, even starting from the first principles of quantum mechanics.
References[1] T. Sato, Y. Orimo, T. Teramura, O. Tugs, and Kenichi L. Ishikawa, arXiv:1804.08246 (2018)[2] K. L. Ishikawa, Y. Shinohara, T. Sato, T. Otobe, arXiv:2003.14090 (2020)[3] Y. Kobayashi, et al., IEEE J. Sel. Topics Quantum Electron. 27, 8900108 (2021)