Theory of Raman scattering by surface polaritons in a four-media system

The method of linear response theory is used to determine the response functions for surface polaritons in a four-media system (or bounded bilayer). The dispersion relation is found when the pole of the derived response function vanishes. The expressions for the scattered intensity for both back and forward scattering are derived. The scattered intensity depends on a polarisation which is the result of the coupling of the incident light to the vibrational coordinates and electric fields associated with electric-dipole-active lattice vibrations in the bilayer. Expressions for the Raman cross section by surface polaritons in the four media system are derived for both back and forward scattering. Numerical results are presented by using parameters for a sapphire substrate-GaP-GaAs bilayer-vacuum system.