Abstract: In this report,, it is shown that by applying Ewald-Oseen'g extinction theorem to a slab optical waveguide, the distribution of the guided-wave fields and the mode condition can be systematically obtained. Besides, it can be seen that the guided-waves are essentially eigen-states of the dipolar field of the waveguide. The characteristic properties of the optical guided-waves can be interpreted in terms of our elementary-excitation hybridization scheme.