Numerical Simulation of Ultra-short Laser Pulses Propagation in Gas Media

<p><span>Over the past ten years, important theoretical and practical results have been obtained in the field of interaction of high-power ultra-short laser pulses with solid transparent media. These results are significant for nonlinear optics and laser physics and are of practical interest for the development of femtosecond laser technology in sensing the environment, in the management of electrical discharge, in microphotonics.</span></p><p><span>However, many of the physical aspects of the supercontinuum generation and distribution of high-power femtosecond and attosecond laser pulses in an optically transparent gas media are not clear and require a detailed theoretical study.</span></p><p><span>Main objectives of the present study are the numerical simulation of high-intensity femtosecond pulses in the air, given the stimulated Raman scattering (SRS) and the stimulated Raman self-mode (SRSM) on pure nitrogen and oxygen molecules as well as on their mixtures.</span></p><p><span>Computer programs have been developed for solving nonlinear equations associated with the SRS and SRSM on the basis of a semi-classical energetic and wave theory with the help of numerical methods. </span></p><p><span>All calculations were made in the Visual Studio C ++ and Java programming environment. </span></p><p><span>The SRS mode for the distance of up to 5m for the main components of the air - nitrogen (78%) and oxygen (21%), in addition to the dynamics of the change of the pulse energy for different initial values have been calculated. </span></p><p><span>The propagation of SRMS laser pulses (λ=400, 800 nm; τ= 14, 20 fs) with positive chirp was numerically investigated for pulse energies 2π, π, π/100 and βz = 0.5, 1.0, 1.5.</span></p><p><span>The results obtained show that the dynamics of pulse propagation in SRMS mode is nonlinear in the pulse shape and spectrum. </span></p><p><span>It was estimated that the calculation results in energetic and wave models for </span>β<span>z≤1.5 are similar.</span></p>