Characteristics of modes of the planar waveguide with thin walls, which are made from nonlinear media, are studied. The effect of the conversion of a mode from one set to another is considered. This effect may occur if parameters of the waveguide or transmitted power are varied. It is shown that the effect of the guided or leaky modes «disappearance» can arise when the field amplitudes increase, i.e., high powers launched into such a structure can suppress the modal propagation.
