CONVERSION BETWEEN POLARIZATION STATES AT THE SINUSOIDAL BOUNDARY OF A UNIAXIAL CRYSTAL

The conversion between polarization states upon reflection on the weakly corrugated interface between uniaxial crystals and isotropic media is studied by means of a model based on the Rayleigh hypothesis. We deal with sinusoidal gratings with the wave vector of the incident light being perpendicular to the grating grooves. Two situations are considered: (i) incidences from an isotropic, lossless dielectric onto a crystal and (ii) from a crystal onto a metal. The results show that in the first case total reflection plays an important role in polarization conversion, even for flat interfaces, where nearly 54% of s-to-p conversion can be attained, and that a weak corrugation can increase this value slightly. On the other hand, for metal-crystal interfaces illuminated under conditions of resonant excitation of surface plasmons, corrugation has a much stronger effect in the change of polarization of the incident wave. It is shown that the efficiency of conversion between ordinary and extraordinary modes can increase more than 250 times when the value of the groove height-to-period ratio is varied from 0 to 0.2. This effect is accompanied by a strong absorption in the metal and by narrow dips in the curves of copolarized efficiencies as functions of the angle of incidence.