ENHANCEMENT AND QUENCHING OF BERREMAN POLARITONS IN SIO2 TIO2 AND AL2O3/PT SUPERLATTICES/

Optical properties of SiO2TiO2 and Al2O3/Pt superlattice films have be en studied by infrared ellipsometry with emphasis on the reststrahlen bands of the silicon and aluminum oxides. The SiO2 and TiO2 thicknesse s were 5.0 and 3.2 nm, respectively, while the Al2O3 and Pt layer thic knesses were 10.0 and 2.5 nm. The presence of TiO2 layers created a pr onounced spectral feature just above the SiO2 LO frequency. The result s were analyzed by means of transfer matrices. It was found that a sup erlattice film is capable of introducing sharp spectral features at wa velengths where the refractive index of the substrate is close to unit y and the absorption coefficient is small. The validity of effective p ermittivity calculations is investigated for insulator/insulator and i nsulator/metal superlattices, and the influence of Berreman polaritons is discussed. We also address the question of how the strength of the se polaritons may be suppressed in certain configurations.