New Routes for Label-Free Super-Resolution Microscopy and Attosecond Science via Transient High-Harmonic Generation

While the upconversion of infrared driving lasers into soft-X-ray pulses by high-harmonic generation (HHG) <i>in gases</i> has become an established technique for attosecond science and nanoscale imaging [1-3], HHG <i>in solids</i> is less explored. Gas-phase HHG is highly sensitive and thus controllable with regards to the microscopic generation mechanism, and the macroscopic buildup of emission via phase matching [4,5]. Parallels between solid and gas-phase HHG suggest that solid-state HHG may be controlled in similar manners, which would enable a generally applicable all-optical light switch with wide application potential.<br/><br/>In this talk I will introduce femtosecond resolved solid-state HHG and highlight the applications of solid-state HHG for metrology, spectroscopy and imaging with recent examples from our group.<br/>On the nanoscale, we controlled HHG via engineering the surface topography of solids, which in turn demonstrates how solid HHG can be used for metrology on surfaces and tailored as a light source [6].<br/>On the femtosecond time scale, we used the sensitivity of HHG to electronic band structure to follow ultrafast phase transitions in strongly correlated materials [7], and photocarrier dynamics in perovskites [8].<br/>While the first set of measurements mentioned above showed nanoscale sensitivity, the second set of experiments demonstrated that photoexcitation can be used to control light emission via solid-state HHG.<br/>Combining both efforts, I will outline and show first results how ultrafast control of solid HHG enables harmonic deactivation microscopy (HADES) - a label-free super-resolution microscopy below the diffraction limit of light [9].<br/><br/>Thinking ahead, the development of these techniques may enable 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.<br/><br/><u>References:</u><br/>[1] P.M. Kraus, H.J. Wörner, Angewandte Chemie International Edition 57, 5228 (2018).<br/>[2] P.M. Kraus, M. Zurch, S.K. Cushing, D.M. Neumark, S.R. Leone, Nature Reviews Chemistry 2, 144 (2018).<br/>[3] P.M. Kraus et al., Science 350, 790 (2015).<br/>[4] S. Roscam Abbing, F. Campi, F.S. Sajjadian, N. Lin, P. Smorenburg, P.M. Kraus, Physical Review Applied 13, 054029 (2020).<br/>[5] S. Roscam Abbing, F. Campi, A. Zeltsi, P. Smorenburg, P.M. Kraus, Scientific Reports 11, 24253 (2021).<br/>[6] S.D.C. Roscam Abbing, et. al., P.M. Kraus; Physical Review Letters 128, 223902 (2022).<br/>[7] Z. Nie et al., Peter M. Kraus, Physical Review Letters, in review (2023).<br/>[8] M. v.d. Geest, J.J. de Boer, K. Murzyn, P. Juergens, B. Ehrler, P.M. Kraus, Journal of Phys. Chem. Lett., in review (2023).<br/>[9] K. Murzyn et al., P.M. Kraus, in preparation.