Filters

20202

More filters

2021 - 20222
Reset filters

Settings

End date: 2024 × Start date: 2020 × End date: 2023 × Start date: 2020 × Type: Article × Subject: filamentation × WGL Institute: MBI ×

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Terahertz pulse generation by two-color laser fields with circular polarization
    ([London] : IOP, 2020) Tailliez, C.; Stathopulos, A.; Skupin, S.; Buožius, D.; Babushkin, T.; Vaičaitis, I.; Bergé, L.
    We study the influence of the polarization states of ionizing femtosecond two-color pulses on the emitted terahertz radiation in gases. A local-current model and plane-wave evaluations justify the previously-reported impact on the THz energy yield and a (almost) linearly-polarized THz field when using circularly-polarized laser harmonics. For such pump pulses, the THz yield is independent of the relative phase between the two colors. When the pump pulses have same helicity, the increase in the THz yield is associated with longer ionization sequences and higher electron transverse momenta acquired in the driving field. Reversely, for two color pulses with opposite helicity, the dramatic loss of THz power comes from destructive interferences driven by the highly symmetric response of the photocurrents lined up on the third harmonic of the fundamental pulse. While our experiments confirm an increased THz yield for circularly-polarized pumps of same helicity, surprisingly, the emitted THz radiation is not linearly-polarized. This effect is explained by means of comprehensive 3D numerical simulations highlighting the role of the spatial alignment and non-collinear propagation of the two colors. © 2020 The Author(s). Published by IOP Publishing Ltd on behalf of the Institute of Physics and Deutsche Physikalische Gesellschaft.
  • Thumbnail Image
    Item
    Influence of tunnel ionization to third-harmonic generation of infrared femtosecond laser pulses in air
    ([London] : Macmillan Publishers Limited, part of Springer Nature, 2020) Tamulienė, Viktorija; Juškevičiūtė, Greta; Buožius, Danas; Vaičaitis, Virgilijus; Babushkin, Ihar; Morgner, Uwe
    Here we present an experimental as well as theoretical study of third-harmonic generation in tightly focused femtosecond filaments in air at the wavelength of 1.5μm. At low intensities, longitudinal phase matching is dominating in the formation of 3rd harmonics, whereas at higher intensities locked X-waves are formed. We provide the arguments that the X-wave formation is governed mainly by the tunnel-like ionization dynamics rather than by the multiphoton one. Despite of this fact, the impact of the ionization-induced nonlinearity is lower than the one from bound–bound transitions at all intensities. © 2020, The Author(s).