LAUSR

A model is proposed for the nonlinear response of a medium in which the permittivity depending on the field intensity is instantaneously switched when the field amplitude reaches a certain value. The propagation of a self-channeled light beam in a medium with such a nonlinearity and with the same type of the Kerr response (self-focusing or defocusing) is considered. It is shown that when the switching field exceeds the threshold value, a symmetric finite-length region (domain) with different optical properties is formed along the beam channel. Three cases of combination of the nonlinearity signs and the values of the effective refractive index are considered. In the focusing medium, the power of radiation propagating along the interface is higher than in the defocusing medium. In the defocusing medium, there exists a threshold value of the total luminous energy flux, beginning with which self-localization can occur, when the values of the effective refractive index lie between the unperturbed dielectric constants of the medium and of the domain.