Browsing by Author "Graini, Leila"

Filter results by typing the first few letters
Now showing 1 - 2 of 2
  • Thumbnail Image
    ItemOpen Access
    Spatial beam self-cleaning accompanied by self-similar propagation in few-mode graded-index fiber
    (Optica Publishing Group (formerly OSA), 2023-07-20) Graini, Leila; Ortaç, Bülend
    We numerically investigated a nonlinear Kerr beam self-cleaning (KBSC) dynamics accompanied by self-similar propagation regimes, which leads to single-mode parabolic pulse reshaping and simultaneously high beam quality based on KBSC, for special distributions of initially excited modes in graded-index multimode fiber (GRIN-MMF). We coupled a Gaussian pulse at 1060 nm, with 100 fs duration, into GRIN-MMF supporting 10 modes that fall into four discrete mode groups. As a result, by using initial powers below the KBSC threshold reported in the literature, the output spatial beam evolves from a speckled pattern into a bell-shaped beam; hence, the generated parabolic pulse is mainly carried by the fundamental mode, which is boosted by the KBSC process. We also provide promising indications for KBSC on different higher-order modes.
  • Thumbnail Image
    ItemOpen Access
    Spatiotemporal evolutions of similariton pulses in multimode fibers with Raman amplification
    (MDPI AG, 2021-09) Graini, Leila; Ortaç, Bülend
    This paper aims to pave the way towards the demonstration of spatiotemporal similariton pulses’ evolution in passive multimode fibers with Raman amplification. We numerically present this issue in graded-index and step-index multimode fibers and provide a first look at the complex spatiotemporal dynamics of similariton pulses. The results showed that the similariton pulses could be generated in both multimode fibers. The temporal and spectral evolution of the pulses can be characterized as parabolic shapes with linear chirp and kW peak power. By compressing these, high-energy femtoseconds pulses can be obtained, starting initial picosecond pulses. A spatial beam profile could be preserved in both multimode fibers with the most energy coupled to the fundamental mode. Specifically, the similariton pulses’ generation with Raman amplification in a graded-index multimode fiber improves the spatial beam self-cleaning process under the different initial modes’ excitation. The observation of a new beam self-cleaning process is another attractor feature of propagation in graded-index multimode fibers.