Polarization dependence of surface plasmon polariton emission

Surface plasmon polaritons (SPP's) need specific conditions for excitation by photons. In order to fulfill the dispersion relation of the SPP's the photons are required to approach the metal interface from an optically denser medium. For this an attenuated reflection setup (ATR) of a so-called Kretschmann type is used. The excited plasmon may decay by the emission of photons with the same angle with respect to the surface normal. Deliberately using rough metal films the surface plasmon polariton is elastically scattered at the interface. This results in a partial loss of coherence of the reemitted photons. While the angle in respect to the surface normal is conserved, a fraction of the emitted photons leave the plane of incidence, resulting in the so-called ATR cone. Upon analysis of the polarization dependence of light from the ATR cone, an exceptionally clear polarization dependence has been found. The observed behavior is the complete linear polarization of the light in the plane of emission, thus resulting in continuously changed polarization in respect to the polar coordinates within the ATR ring.