Coupled phonon-photon excitation field structure and dispersion in bin
ary semiconductor superlattices are studied using a local theory with
retardation. The material layers are characterized by the frequency-de
pendent isotropic dielectric permittivities. Numerical calculations ha
ve been carried out for GaAs/AlAs superlattices with the layer thickne
ss ratio d(1)/d(2)<1 and d(1)/d(2)>1 in the case of in-plane propagati
on of p-polarized electromagnetic waves. Seven main dispersion branche
s and two series of additional ones related to confined modes are obta
ined. The latter are found to exist just below the transverse optical
phonon frequencies of constituent materials. The branches characterize
d by different types of field symmetry are found to intersect in the a
bsence of damping. The conditions of the crossing points existence are
estimated.