In the present paper, the propagation of an electromagnetic beams in nonlinear dielectric slab waveguides is deeply and parametrically investigated. The nonlinear film layer is sandwiched between either linear or nonlinear cover and substrate layers. Two nonlinear slabs are processed mainly Gallium Aluminum Arsenide Ga1-xAlxAs and Lithium Niobate LiNbO3 where x is the Al concentration. The nonlinear coefficient of the refractive index is computed on the bases as simple quantum mechanical formula to obtain a soliton pulse transmission. The powers in the three layers (cover, film, and substrate) are computed under different thermal and spectral conditions. The nonlinear electric field equation is cast under a normalized dimensionless form. It is found that the total chromatic dispersion coefficients of the films decrease numerically as the optical wavelength increases, and consequently both the bandwidth and the transmitted soliton bit rate increase. It is also found that LiNbO3 waveguide possesses better performance if compared to AlGaAs waveguide in addition to  its thermal stability. Also, the confinement factor increases as the refractive index difference increases.