Optical anisotropy in superlattices as a consequence of dielectric mismatch

The “bulk‐slab” continuum model for the dielectric function of a superlattice is reconsidered. It is demonstrated how the optical anisotropy of the effective medium depends on the dielectric mismatch between the layers. As examples the dielectric mismatch and layering‐induced anisotropy are studied for both phonon and electronic interband excitations in GaAs/AlAs and GaSb/InAs superlattices. It turns out that the dielectric mismatch and hence the anisotropy for phonon excitations is large in comparison to that for electronic interband transitions. Angular dependencies of longwavelength optical phonons for long period superlattices are derived from the angular dependence of the dielectric function of the extraordinary ray in the effective medium.