The authors present experimental as well as theoretical data for the linear optical response of symmetrically strained Ge4Si6(001) superlattices. Ab initio calculations show that the superlattice considered has a direct gap at about 1.1 eV. The lowest direct transitions are dipole allowed, although they are rather weak. The complex dielectric function has been measured with a rotating analyser ellipsometer. Excellent agreement of the experimental second-derivative spectrum d2 in 2/d omega 2 with the theory is obtained after the calculated in 2( omega ) has been convoluted with a Lorentzian to include effects of lifetime broadening, both for the shape and position of bulk-like and for new superlattice-like transitions. A detailed analysis of the observed structures in terms of interband transitions is given.
 

Materials Science & Engineering B, 43 233-6, 1991.