arXiv subjects

Lucie Jurkovičová

Publications and source records attributed to Lucie Jurkovičová.

6 recordsLinked to original sources

arXiv2026

THz emission from multiply ionized laser plasma

Studies employing nonlinear interactions of ultrashort THz pulses with matter are becoming a promising scientific research field enabling access to ultrafast dynamics unattainable by other methods. To enter this regime, THz pulses with energy ranging from hundreds of $μ$J to the mJ level are necessary. However, techniques that provide pulses with such energy levels are still not widely established. Upscaling methods of laser-solid interaction is limited by the damage threshold of materials, while the mechanism of THz generation from high-intensity laser-gas interactions is not fully understood yet. Here, we establish the photocurrent model of laser-driven plasma THz generation in the unexplored high-intensity regime by accounting for high-ionization states of the target gas. Our model shows excellent agreement with experimental observations, providing a clear explanation of phenomena in both spectral and temporal domains. Moreover, in such a regime it explains a newly observed significant increase in conversion efficiency from laser to THz. In the experiments, we achieved a generation of 0.2 mJ THz pulses, driven by a Ti:sapphire laser with a conversion efficiency exceeding 1 %.

physics.plasm-ph↗

arXiv2026

Floquet-engineering unveiled by high-harmonic generation

Ultrafast optical control of solids has uncovered new phenomena and advanced non-equilibrium condensed matter physics, where photon dressed electronic states - Floquet Bloch states (FBSs) - emerge under a strong oscillating laser field, also known as Floquet engineering. Although FBSs have been extensively investigated using time and angle resolved photoemission spectroscopy, direct evidence of their role in high-harmonic generation spectroscopy (HHGS) has remained elusive. Here, we present combined experimental and theoretical evidence that FBSs can be probed by HHG emission in the wide-bandgap solid magnesium oxide (MgO) driven by few cycle near infrared pulses. Experimentally, we observe clear evidence of FBSs in the HHG yield dependence on the crystal orientation. This specific feature is attributed to nonadiabatic coupling between FBSs and conduction bands near the Brillouin zone edge, where the strong laser field transiently breaks time reversal symmetry. We have confronted the experimental findings with numerical solutions of the time dependent Schrödinger equation, which reproduce the new feature and confirm its Floquet origin. The theoretical results show a coupling inducing a local band structure renormalization and Floquet like hybridization under strong field excitation. It also shows that FBS nonadiabatic dynamics persist in the strong field regime, establishing HHGS as a powerful probe of ultrafast light induced band hybridization in solids.

quant-ph↗

arXiv2026

2D quantum-path interference in high-harmonic generation driven by highly-bichromatic fields

We experimentally observe a new type of quantum-path interference, in two-dimensions (2D-QPI), in high-harmonic generation (HHG) driven by an orthogonally-polarised highly-bichromatic field. This regime is marked by comparable intensities of the two orthogonal colours. In this highly-bichromatic regime, we demonstrate that 2D-QPI is encoded in the measured harmonic intensity modulations with respect to the relative phase of the two-colour field. The modulations of the odd-order harmonics show a monomodal behaviour, whereas the even harmonics are modulated in a bimodal structure. Our calculations using the strong-field approximation and saddle-point method disentangle contributions from multiple quantum orbits in this HHG regime, revealing that the dipole response for both odd and even harmonics inherits the dynamic symmetry of the orthogonally-polarised driving field. This new type of 2D-QPI offers a novel route to HHG spectroscopy of attosecond electron dynamics by lifting up the dimensionality of the quantum paths involved in the interference.

quant-ph↗

arXiv2025

XUV fluorescence as a probe of interatomic Coulombic decay of resonantly excited He nanodroplets

Superfluid He nanodroplets resonantly excited by extreme ultraviolet (XUV) pulses exhibit complex relaxation dynamics, including the formation of metastable excited He$^*$ atoms trapped in bubbles, the desorption of excited atoms from the droplet surface, and autoionization via interatomic Coulombic decay (ICD). Irradiation with intense infrared pulses can trigger avalanche ionization, leading to the formation and subsequent expansion of a He nanoplasma. Here, we introduce a novel approach to probe the ICD dynamics over timescales spanning femtoseconds to nanoseconds. Our method exploits the efficient ignition of a nanoplasma through tunnel ionization of excited helium atoms attached to the droplets and the detection of XUV fluorescence emitted from the resulting nanoplasma. Using quantum mechanical and classical calculations, we interpret the nanosecond fluorescence decay as a signature of ICD mediated by He$^*$ freely roaming on the nanodroplet surface.

physics.atm-clus↗

arXiv2024

Monochromatic high-harmonic generation by Bessel-Gauss beam in periodically modulated media

High harmonic generation (HHG) has become a multipurpose source of coherent XUV radiation used in various applications. One of the notable aspects of HHG is its wide spectrum consisting of many harmonic orders. This might represent a bottleneck in HHG utility for applications requiring a single wavelength. We propose a method to generate radiation consisting of a single high-order harmonic frequency employing Bessel-Gauss driving beam and a periodically modulated gaseous medium. We validate it by analytical calculations and numerical simulations. Our method provides a way to generate monochromatic harmonic radiation directly from the source without the need for additional monochromatizing optics. Thus, it represents a substantial enhancement of the flux and simplification of the setup for numerous applications requiring monochromatic short-wavelength radiation.

physics.optics↗

arXiv2023

Bright continuously-tunable VUV source for ultrafast spectroscopy

Ultrafast electron dynamics drive phenomena such as photochemical reactions, catalysis, and light harvesting. To capture such dynamics in real-time, femtosecond to attosecond light sources are extensively used. However, an exact match between the excitation photon energy and a characteristic resonance is crucial. High-harmonic generation sources are exceptional in terms of pulse duration but limited in spectral tunability in the VUV range. Here, we present a monochromatic femtosecond source continuously tunable around 21 eV photon energy utilizing the second harmonic of an OPCPA laser system to drive high-harmonic generation. The unique tunability of the source is verified in an experiment probing the interatomic Coulombic decay in doped He nanodroplets across the He absorption bands. Moreover, we achieved intensities sufficient for driving non-linear processes using a tight focusing of the VUV beam. We demonstrated it on the observation of collective autoionization of multiply excited pure He nanodroplets.

physics.atom-ph↗