Effects of the Film Thickness on the Fields of Nonlinear-Cladding Optical Waveguides With Butt-Coupled Linear Waveguides

Effects of the film thickness of nonlinear-cladding optical waveguides on the evolution of fields at medium power levels are investigated numerically. The analysis method is based on mode matching of local normal modes of bounded waveguides. For the analyzed waveguide structures and power levels, the path of a beam winds between the film and the nonlinear cladding or in the film. Fields travel in the nonlinear cladding in the case of a thin film, whereas fields are confined to the film in the case of a thick film. The lateral shift of a butt-coupled linear waveguide toward the substrate makes a beam emit toward the nonlinear cladding. The excitation from a linear waveguide whose film is thicker than that of a nonlinear waveguide is effective in causing spatial soliton emission. Saturation and linear absorption weaken the winding of a path or decrease the angle of emission.