Dielectric and Magnetic Properties of Superlattices.

Available from UMI in association with The British Library. Requires signed TDF. The coupling of the classical electromagnetic field with the phonon field in semiconductor superlattices is studied. It is shown from the exact equations for transverse electromagnetic waves propagating in an infinitely extended superlattice that, in the long-wavelength limit, the superlattice has the optical properties of an unconventional uniaxial medium, with the optic axis normal to the layer planes. This result is used to derive the frequency dependence of the superlattice's effective dielectric-tensor components. By using the effective medium description, the dispersion relation for bulk phonon-polaritons is derived along with the dispersion relation for surface polaritons at the interface of a superlattice and an isotropic, homogeneous medium. The effective-medium description is then used to interpret far-infrared normal incidence reflectivity measurements from a GaAs/Al_{rm x}Ga_{rm 1-x} As multi-quantum well (MQW) structure. A least -squares fit of theory to experimental data gives values for the reststrahl-region parameters of the GaAs and Al _{rm x}Ga _{rm 1-x}As layers. Calculations are then performed for the theory of far-infrared attenuated total reflection (ATR) from semiconductor MQW's. Features in the ATR curves for p -polarized incident light are identified as corresponding to surface or guided-wave polaritons. Curves for s-polarization show only guided-waves. Comparisons are given of theoretical ATR curves with recently obtained experimental curves. The coupling of electromagnetic waves with spin -waves in magnetic superlattices is also considered. The dispersion relation for bulk TE and TM magnetic-polaritons are derived and from the full dispersion relation for TE -modes, a long-wavelength description of the magnetic superlattice is given. An effective magnetic permeability tensor for the superlattice is derived and these results are used to obtain long-wavelength bulk dispersion relations. Green functions for the magnetic superlattice are derived and possible applications for them are discussed.