Conférence : « Nanoscopie ultrarapide par génération de hautes harmoniques contrôlées optiquement à partir de solide »

Professeure qui invite : Heide Ibrahim

Biographie :

Peter Kraus is the group leader of the “High-harmonic generation and EUV science” group at the Advanced Research Center for Nanolithography (ARCNL), and associate professor of physics at the VU University Amsterdam. Since July 2024, Peter has also been part of the ARCNL management team as head of the metrology department. Peter’s research interests lie in developing extreme ultraviolet (EUV) and highly nonlinear light sources from gas and solid-state high-harmonic generation and apply them for ultrafast spectroscopy and nanoscale metrology experiments with relevance to nanolithography. 

Prior to joining ARCNL/VU in 2018 as group leader/assistant professor, Peter Kraus worked at the University of California, Berkeley (USA) on the development of new experimental techniques for investigating attosecond phenomena in solid-state materials. Peter obtained his PhD at ETH Zurich (Switzerland) in 2015. Here, he developed and advanced the techniques of high harmonic-spectroscopy for investigations of electronic and nuclear structure and dynamics of molecular systems.

Amongst other, Peter has obtained an ERC Starting Grant (2022) from the European Research Council (ERC), as well as the VENI (2018) and VIDI (2023) grants from the Dutch Research Council (NWO).

Résumé :

The highly complex collective electron-dynamics in strongly correlated materials mandates experimental techniques with sub-fs temporal and nanometer spatial resolution. While a plethora of techniques exists, true nanometer imaging on fs or even sub-fs timescales remains elusive. Such techniques are required to follow the collective dynamics of electrons in strongly correlated materials in real time, which drive ultrafast phase transitions that are accompanied by technologically relevant order-of-magnitude resistivity switches. High-harmonic generation (HHG) in solids has emerged 14 years ago and found many applications, including as a probe in ultrafast spectroscopy experiments. We recently conducted a thorough analysis of current literature, which suggests that optical excitation during or prior to HHG generally suppresses HHG – if optimized with near-100% efficiency. [1] This constitutes an unparalleled control mechanisms over light emission.

In this talk, I will present the mechanisms behind this optical suppression of solid-state HHG, and our ongoing research to use this light switch for sub-fs super-resolution nanoscale imaging by HHG from correlated materials. In particular, I will present a number of key experiments on our roadmap towards this goal. On the femtosecond time scale, we used the sensitivity of HHG to electronic band structure to follow ultrafast phase transitions in strongly correlated materials [2], and photocarrier dynamics in perovskites. Similarly, we studied a number of other semiconducting and insulating materials. These studies now provide a general understanding of the microscopic mechanisms behind suppression of HHG by optical control pulses.

We use this general suppression mechanisms to spatially confine HHG from solids by pre[1]exciting materials with an orbital-angular-momentum carrying pulse, which thus spatially confines HHG to below the diffraction limit. This enables HArmonic DEactivation microScopy (HADES) – a label-free super-resolution microscopy below the diffraction limit of light [3]. Thinking ahead, the development of these techniques may enable label-free resolution on the nanometer and femto- to attosecond scale fitted into a regular microscopy setting, with application potential ranging from strongly correlated materials to semiconductor metrology, photosynthetic processes, and medical imaging.

References:

[1] P. v. Essen, Z. Nie, B. de Keijzer, P.M. Kraus, ACS Photonics 11, 1832 (2024)
[2] Z. Nie et al., Physical Review Letters 131, 243201 (2023).
[3] K. Murzyn, M.v.d. Geest, L. Guery, Z. Nie, P.v. Essen, S. Witte, P.M. Kraus, Science Advances 10, eadp3056 (2024)

*Le séminaire sera présenté en anglais.