Аннотация:Here we present the result of theoretical investigations of a single atom interaction
with a multicolor laser field formed by an arbitrary number of the components with an arbitrary orientation of polarization vectors. The developed theory is non-perturbative and valid in the whole sub-relativistic region of the laser field strength. It results in a new mechanism of a nonlinear atomic response which is mainly due to the light-induced anisotropy of an electron wave function but not by electron transitions between the free atom eigenstates. For example, the terahertz (THz) emission in ionization-free regime is interpreted without exploiting the plasma nonlinearities (usually the four-wave mixing rectification process). The numerical experiment simulates an Argon atom interaction with the fundamental and the second harmonic of Ti:Sapphire laser. It is shown that the spectral width and efficiency of the THz emission depend nonlinearly on the parameters of the multicolor laser field.