Application of Cohen Distribution Functions for Time-Frequency Analysis of Chirped Laser Beams

Based on the Cohen distribution function and physical spectrum concept, a new algorithm for numerical analysis of the time-frequency distribution of photon flux density of a chirped laser beam has been developed. This made it possible to use the well-known photon transport equation for modeling the evolution of not only spatial and energy, but also spectral characteristics of radiation in high-power laser systems. This approach allows us to solve the problem of "negative probability" arising when using the Wigner distribution function for non-Gaussian laser beams. Comparison of the obtained data with the results of experiments and numerical modeling of amplification of chirped laser beams in the XeF(C-A) gas amplifier of the THL-100 laser system proved applicability of the model.