Nonparaxiality of dissipative optical solitons

A version of the perturbation theory is developed for determining the field distribution of spatial solitons with a 2D transverse profile in a medium with saturable absorption and gain in the case of small deviations from paraxial conditions. Starting from the unperturbed paraxial soliton with the linear polarisation of radiation, an approximate master equation is derived for transverse components of the electric field in the case of wide solitons. It is shown that its solution represents a stable weakly nonparaxial dissipative optical vector soliton with an axially asymmetric field distribution.