Nonlinear Waves in Saturable Self-Focusing Thin Films Bounded by Linear Media

Nonlinear guided wave behavior in the symmetric and asymmetric versions of the waveguide is studied. The waveguides are made to be cut off at low field intensities by a step-index decrement in the dielectric constant of the film relative to those of the bounding media. The influence of this decrement on solutions of the TE0 mode is calculated. The mode index variation of the asymmetric solution in the symmetric waveguide is shown to depend strongly on the index decrement as well as the saturation level. By making the media bounding the film have sufficiently different dielectric constants, only one solution is shown to be obtainable. This solution is followed both on the locus diagram relating the field intensities on the film boundaries and also on the dispersion plots. It is verified that this solution transforms into that of the three-layer linear step-index waveguide in which the film is made homogeneous at high field intensities in accordance with the saturation form used in the work.