About group velocity of electromagnetic wave in linear isotropic homogeneous medium

Current works, devoted to changing of group velocity of laser pulses by spatial structuring laser beams, allow us to solve only direct problem -- to define group velocity using information about wave structure. We propose a math model of wave propagation based on using real functions of spatial distributions of amplitude, phase and group velocity, which allows to solve as direct as inverse problem -- to define spatial structure of beam using data about necessary group velocity [1]. Applying new model to experimental data from, for example, [2,3] shows high quality results. Practical applicability of our results are also can be in future confirmed in experiments with spatial light modulator. [1] M. K. Galinsky, V. V. Rumyantsev, Problems of Artificial Intelligence (ISSN: 2413-7383) 10, 14 (2018). [2] D. Giovannini et al., Science. 347, 857 (2015). [3] N. D. Bareza, N. Hermose, Sci. Rep. 6, 26842 (2016).