Photons traveling at the speed of light in a two-level atomic medium as a source of Cherenkov radiation cones

This paper discusses the mechanisms responsible for the emergence of a cone radiation structure observed in the nearly resonance interaction of a laser radiation beam (of frequency $\nu$) with a two-level atomic medium (the case $\nu<\nu_{01}$, where $\nu_{01}$ is the energy-level transition frequency). Use is made of a model which takes into account the axial symmetry of laser radiation beams and the fact that the transverse intensity distribution of the laser beams is Gaussian, and therefore the probability of nonlinear optical processes affecting the propagation of light is maximal on the axis of the laser beam.