Universität Stuttgart

Permanent URI for this communityhttps://elib.uni-stuttgart.de/handle/11682/1

Browse

Filters

2022 - 20244

Settings

Author: search.filters.author.Graf, ThomasSubject: search.filters.subject.600

Search Results

Now showing 1 - 4 of 4
  • Thumbnail Image
    ItemOpen Access
    Generation of a radially polarized beam in a polycrystalline ceramic Yb:Lu2O3 thin-disk laser
    (2023) Didychenko, Denys; Esser, Stefan; Beirow, Frieder; Savchenko, Anton; Pruss, Christof; Graf, Thomas; Abdou Ahmed, Marwan
    AbstractWe report on the generation of a continuous-wave (CW) radially polarized beam with an Yb:Lu2O3 polycrystalline ceramic disk in a thin-disk laser (TDL) oscillator. A circular grating-waveguide mirror (CGWM) with a high polarization discrimination given by a reflectivity difference between the two orthogonal polarization states of 44.6% was used as a polarization-selective cavity end-mirror. An output power of 175 W was achieved with an optical efficiency of 39.6%. A high degree of radial polarization of 96.2% and a beam propagation factor of M2hor. = 2.05 and M2ver. = 2.32 were measured at the maximum output power.
  • Thumbnail Image
    ItemOpen Access
    Experimental analysis on CPA-free thin-disk multipass amplifiers operated in a helium-rich atmosphere
    (2022) Bienert, Florian; Loescher, André; Röcker, Christoph; Graf, Thomas; Abou Ahmed, Marwan
    Es wird der Einfluss von Helium als atmosphärisches Gas in Scheibenlaser-multipass-Ultrakurzpulsverstärkern untersucht.
  • Thumbnail Image
    ItemOpen Access
    Detrimental effects of period-chirped gratings in pulse compressors
    (2023) Bienert, Florian; Röcker, Christoph; Dietrich, Tom; Graf, Thomas; Abdou Ahmed, Marwan
  • Thumbnail Image
    ItemOpen Access
    Impact of repetitive, ultra-short soft X-ray pulses from processing of steel with ultrafast lasers on human cell cultures
    (2024) Holland, Julian; Lungu, Cristiana; Weber, Rudolf; Emperle, Max; Graf, Thomas
    Ultrafast lasers, with pulse durations below a few picoseconds, are of significant interest to the industry, offering a cutting-edge approach to enhancing manufacturing processes and enabling the fabrication of intricate components with unparalleled accuracy. When processing metals at irradiances exceeding the evaporation threshold of about 10 10 W/cm² these processes can generate ultra-short, soft X-ray pulses with photon energies above 5 keV. This has prompted extensive discussions and regulatory measures on radiation safety. However, the impact of these ultra-short X-ray pulses on molecular pathways in the context of living cells, has not been investigated so far. This paper presents the first molecular characterization of epithelial cell responses to ultra-short soft X-ray pulses, generated during processing of steel with an ultrafast laser. The laser provided pulses of 6.7 ps with a pulse repetition rate of 300 kHz and an average power of 500 W. The irradiance was 1.95 ×10 13 W/cm 2 . Ambient exposure of vitro human cell cultures, followed by imaging of the DNA damage response and fitting of the data to a calibrated model for the absorbed dose, revealed a linear increase in the DNA damage response relative to the exposure dose. This is in line with findings from work using continuous wave soft X-ray sources and suggests that the ultra-short X-ray pulses do not generate additional hazard. This research contributes valuable insights into the biological effects of ultrafast laser processes and their potential implications for user safety.