A series of five short‐period (InAs)6/(AlSb)6superlattices, grown either with AlAs‐like, InSb‐like, or alternating interfaces, were studied by means of x‐ray diffraction, high resolution transmission electron microscopy (HRTEM), Raman spectroscopy, photoluminescence and ellipsometry. The combination of these techniques allows us to explain the pronounced differences in the optical and structural properties of both types of interfaces. In samples with an AlAs‐like bottom interface x‐ray, HRTEM and Raman results demonstrate the differing structural quality to be related to inhomogeneous strain relaxation and As intermixing. The energies of the critical points E0, E1and E1+&Dgr;1of the samples with pure AlAs‐like interfaces are shifted by more than 100 meV to higher energies with respect to those of the samples with InSb‐like interfaces. These differences can be understood on the basis of the different interfacial atomic structure and strain in the samples. ©1995 American Institute of Physics.