The existence of localized states at InSb-like interfaces of AlSb/InAs superlattices is predicted using empirical pseudopotential calculations. These predictions are shown to be in agreement with those ofab initiopseudopotential calculations performed using the local density approximation of density functional theory, demonstrating the ability of the empirical approach to describe the microscopic features of the interface. The frequency dependence of the absorption coefficient is calculated for a series of AlSb/InAs superlattices with differing interface configurations, and the role of the interface localization in determining the optical response is identified.