Transformation of the shape and spectrum of femtosecond pulses during propagation in gaseous media

Abstract

<p>Investigation and practical use of the propagation processes of ultrashort pulses of high-power optical radiation in media of various physical nature and composition is of considerable experimental and theoretical interest. However, in order to determine more accurate parameters when obtaining the optimal pulse required for conducting research, it is necessary to understand how the pulse changes as it propagates.</p><p>This paper presents the results of numerical simulation of the propagation of high-intensity ultrashort pulses with a positive and negative chirp in the atmosphere in the regime of stimulated Raman scattering (SRS) and stimulated Raman self-scattering (SRS) on the main components of air - oxygen (21%) and nitrogen (78%), and also mixtures thereof. The calculation was carried out for λ = 400, 800, nm, pulse duration 1–25 fs.</p><p>To obtain the temporal localization of the spectral components of the changes, various types of continuous wavelet transform were used.</p><p>As a result, the structure of changes in the spectrum of the pulse with time was revealed and it was shown that when such a pulse propagates, a transition of photons occurs from the beginning of the pulse to its end with practically no change in energy.</p>