Abstract: Polaritons (TE Mode) in a dielectric planar waveguide has been studied. Taking ionic crystal of CsCl type as an example and using tight-binding approximation, we consider only the Coulomb interaction between electrons in the conduction band and holes in the valence band for nearest-neighbor sites and prove that when we deal with light-matter interaction, the material system can be regarded as an ensemble of a series of polarization wave oscillators. Furthermore, the intensity of oscillators is calculated and the dispersion relation, of the polaritons in a dielectric planar waveguide is worked out. The result shows significant difference from classical single oscillator model. According to our microtheory, the distances between upper dispersion curves of the guided-wave polaritons are larger than those obtained by using classical single oscillator model for several types of dielectrics which have wider energy bands and weaker interaction between electrons.