We demonstrate theoretically and experimentally that initially Gaussian optical beam sent through the (pi) -step phase mask and launched into a thin film of polymer poly(methyl methacrylate) doped with laser dye 4- (Dicyanomethylene)-2-methyl-6-(p-dimethylaminostryl(4H-pyran known as DCM evolves into a spatial structure similar to the dark spatial soliton. This takes place due to the third order nonlinearity associated with the mechanism of unconverted photobleaching of the dye-doped polymer. The result of the structuring of the beam is the formation of a permanent pattern of the refractive index of the film that acts as a channel waveguide trapping a weak Gaussian probe beam coaxial with the main beam. We also demonstrate theoretically the possibility of trapping the probe beam, which propagates in opposite direction at an angle to the main beam. The proposed theoretical model is nonlocal in time and is based on the Shrodinger-type nonlinear propagation equation for the main beam and the propagation equation for the probe beam complemented by the rate equation for the light-induced decrease of the refractive index. The results of this study can find application in optical interconnects and data processing.