Polarization conversion from blazed diffraction gratings

Abstract

Abstract We present experimental evidence for significant levels of surface plasmon-polariton mediated polarization conversion from a blazed surface relief diffraction grating, oriented in a geometry where the in-plane component of the incident wave-vector is normal to the grating Bragg vector. This is a configuration in which no polarization conversion would be expected from a diffraction grating with a profile exhibiting reflection symmetry in the plane normal to its surface. The experimental observations are shown to be consistent with model reflectivities calculated using rigorous conical diffraction theory. We go on to show how the presence of a gap in the surface plasmon-polariton dispersion curve perturbs the observed reflectivities, illustrating the splitting of the surface plasmon-polariton dispersion curve with reciprocal-space maps. Finally we use theoretical modelling codes to explore the effect of changing the blazed grating amplitude on the observed level of polarization mixing, also comparing experimental and theoretical predictions for the variation in polarization conversion as a function of the angle between the in-plane component of the incident wave-vector and the grating Bragg vector.

Keywords

Affiliated Institutions

• University of Exeter GB

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