Our latest publication on high harmonic generation is in Communications Physics (Nature Publishing Group)

Researchers from Charles University and HiLASE Centre have published a joint study on the emission of high harmonics emitted by silicon crystal when irradiated by a few-cycle laser pulse. In this work, the group of Martin Kozak (Charles University) measured the energy of photons emitted during the irradiation in the reflection geometry. This enabled to perform a direct comparison with the predictions based on the time-dependent density functional theory (TDDFT), prepared by Thibault Derrien (HiLASE Centre).

The paper evidences the importance of the carrier-envelope phase and of the crystal’s orientation when using ultrashort pulses. The study supports the importance of Van Hove singularities in the angular distribution of the emitted harmonics. Overall, this work demonstrates that quantum approaches and supercomputing are essential for the development of modern laser technologies.

The paper is available at the following address

Journal: Communications Physics (IF 6.459)

Title: Role of Van Hove singularities and effective mass anisotropy in polarization-resolved high harmonic spectroscopy of silicon

Authors: Suthar, P.; Trojánek, F.; Malý, P.; Derrien, T. J.-Y. & Kozák, M.

TJY Derrien attended Benasque TDDFT conference

T. J.-Y. Derrien attended the “9th Time-Dependent Density-Functional Theory workshop: prospects and applications”, held in Benasque (Spain) from Oct. 24th to Oct. 28th. The workshop gathers actors of the TDDFT community and first-principle computations of laser-irradiated materials.

Dr. Derrien presented results on the modification of band structure of solids upon excitation by intense laser light, developed in the context of the WP1-WP2 of the project BIATRI: No. CZ.02.1.01/0.0/0.0/15_003/0000445 and WP5 of Marie Curie RISE ATLANTIC project No. 823897 (www.atlantic-rise.eu).

Website of the conference

Our Springer book chapter is in production

In November 2021, we announced the submission of a chapter for a book edited by Prof. Razvan Stoian and Prof. Jörn Bonse (https://www.quantumlap.eu/springer-chapter-submitted/). We are excited to announce that the production of the book has started and should be available as hard cover around October 2022. Announcement is available at the following address: https://link.springer.com/book/9783031147517.

We are delighted to be published as the first chapter in the Part dedicated to fundamentals of the laser-matter interaction.

The book contains 33 chapters, organized in 3 main parts. The table of contents is not fully disclosed to avoid issues with Copyright agreement.

  • Ultrafast Laser Nanostructuring – The Pursuit of Extreme Scales
    • Foreword R. Stoian* & J. Bonse*: “Ultrafast Laser Nanostructuring – The Pursuit of Extreme Scales – Foreword”
  • Part I: Fundamental Processes in Laser 2D/3D Nanostructuring
    • Chap. 1: T.J.-Y. Derrien, Y. Levy, N.M. Bulgakova*: “Insights into laser-matter interaction from inside: wealth of processes, multiplicity of mechanisms and possible roadmaps for energy localization”
    • […]
  • Part II: Concepts of Extreme Nanostructuring
  • Part III: Functions and Applications

Krystof Hlinomaz published in Int. J. Heat and Mass transfer (IF 5.5)

In preparation of his PhD thesis, our group member MSc. Krystof Hlinomaz has published in the International Journal of Heat and Mass Transfer (Elsevier, IF 5.5).

The paper establishes an efficient description of damage of lossy metallic films deposited on substrates upon interaction with femtosecond and picosecond laser pulses. The results are demonstrating the role of the choice of substrate, and of the choice of film thickness on the film and substrate modification dynamics.

In comparison to existing studies,

  • this work explores a wide range of sample parameters using high power computing,
  • it provides a predictive and robust model benchmarked using several types of validation:
  • a validation of simplified cases on analytical solutions,
  • a real-time monitoring of the energy conservation of the non-linear system,
  • a validation by direct comparison with well established experimental results of the literature.

The work is useful for improving the precision of laser processing of thin metallic films using femtosecond and picosecond laser pulses.

Title of the study is: “Modeling thermal response of Mo thin films upon single femtosecond laser irradiation: dynamics of film melting and substrate softening”

The paper is available here: 10.1016/j.ijheatmasstransfer.2022.123292.

New conference communications from the group

In June 6th 2022, our PhD student Krystof Hlinomaz presented an oral contribution entitled “Towards description of mechanical damage of thin molybdenum film upon pulsed laser irradiation” at the HPLS&A conference held in Prague.

On July 8th 2022, our student Ghassan Aber presented a poster on DFT modeling of Ag and TiO2, realized under his previous affiliation, at the School of Laser In Materials Sciences (SLIMS) in Venice.

On July 20th 2022, T. J.-Y. Derrien will present an invited talk (30+10 min.) on transient plasmonics at the CECAM workshop “Light-matter interaction and ultrafast nonequilibrium dynamics in plasmonic materials”.

In October 2022, Krystof Hlinomaz will give an oral/poster contribution, and T. J.-Y. Derrien will give oral presentation at the “Multiscale Material Modeling” MMM conference in Baltimore.

Update on computational facilities [updated July 26th]

The group works at the moment using several sources of high power computations:

  • PRACE/DECI: the supercomputer Navigator (12 cores x 164 nodes) has now been fixed and is back online since July 20th, after 3 months of maintenance. This will be available until December 2022.
  • ELI cluster: collaboration with ELI beam-lines supercomputer Eclipse has started, while size of supercomputer is modest (16 cores x 84 nodes) but sufficient for TDDFT.
  • IT4I.cz: A new OPEN project for the Karolina supercomputer (64 cores x 720 nodes) can now be prepared (early August) and will use AMD processors. The tests on AMD have been well conclusive in our recent attempts.
  • BIATRI-SRV: the cluster of the department runs 64 cores and is sufficient for training students on Python, TTM, DFT, PBS, preparing post-processing of data and storing large amounts of simulation results.

Searching for next funding, PRACE DECI ends soon [updated]

The end of current funding is approaching and the group of Ultrafast Photonics is looking for its next funds. Several projects are being drafted with collaborators at the moment.

Regarding high power computation:

  • PRACE DECI Navigator in Portugal suffers from 2nd critical incident in 6 months, leading to present shutdown of the production. Edit: it may come back during week #26.
  • Note that PRACE DECI subprogram will not be renewed, although it was an excellent and modular program that provided nice timeline along with nice resources to research groups like ours.
  • Mitigation procedures are being put in place to maintain obligations regarding collaborations. Edit: ELI beamlines kindly opened their computer to me since June 20th.

Submitted a proposal to the Grant Agency of Czech Republic (GACR)

A period of proposal drafting has started in the department, and the group of Ultrafast Photonics counts on applying to several funding sources this year to secure financial independence for next years.

On April 1st, a proposal to study the transient excitation of electrons in particular kinds of solids was submitted to the national grant agency. The results are usually known in December of the year of submission. Only 2.5 positions would be potentially funded by this proposal, for people who have already been selected. To secure our positions on a longer time, I am presently participating in drafting of other proposals, which larger amount of funds for salaries.