Gyrotropy in superlattices

In concluding we shall consider briefly the calculation of the superlattice linear response with regard to gyrotropy. As before, we assume that the optical properties inside each of the superlattice layers are isotropic. Therefore, for each of the layers with regard to gyrotropy we have (3)  

Since Vy 1,2 x E oc H is continuous at the boundaries of the layers, and V7 is directed along the ax is and, therefore, Ez does not contribute to the last term in (8.35), one obtains 

The last term differs from zero only at the superlattice boundary. 

In conclusion of this section one may say that the linear optics of superlattices bear rich information on the dynamics of interfaces. Such investigations may give an idea of the nature of the interaction of bulk excitations (excitons) with interfaces which manifests itself in additional boundary conditions (ABC) and determines the value of the constant a. Finally, the study of dispersion laws for polaritons in superlattices with semiconductor layer thicknesses small in comparison with the Bohr radius of exciton permits one to follow variations in the properties of excitons. 

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