The basis of “atom in the external field” eigenfunctions to the problem of high harmonic and terahertz radiation generation study

The paper is devoted to the discussion of the main principles of the non-perturbative quantum-mechanical approach to the description of a single atom interaction with multicomponent laser fields. The main advantage of the theory is that the authors use a basis of “an atom in the field” eigenfunctions which are the exact solution of “an atom in the field” boundary value problem the Hamiltonain of which coincides with the one from the Schrodinger equation written in the velocity gauge. The theory is applied to analytical and numerical investigation of the high-order harmonic generation and the terahertz radiation generation phenomena.