Spontaneous down conversion in metal-dielectric interface - a possible source of polarization-entangled photons

Spontaneous down conversion in metal-dielectric interface in case of oblique laser excitation is considered. In this case it is possible to generate pairs of polarization entangled surface plasmon polaritons with high efficiency if to use excitation angle corresponding to the Kretschmann configuration for generated plasmons. The efficiency can be additionally enlarged if to use properly nanostructured metallic film allowing one to directly excite surface plasmon polaritons and to fulfill phase matching condition of them with generated surface plasmon polaritons.