Topological features of polarization ellipse strips built on non-planar contours in the light scattered on a metal nanospheroid

Abstract

Topological properties of optical strips of the vectors determining the polarization ellipse orientation which are constructed on non-planar contours were studied for the electric field reflected from a gold particle of ellipsoidal shape while irradiated by a plane monochromatic wave. The twisting of each optical strip traced near the particle can be characterised by the sum of the intrinsic twist index of the strip and writhe and full geometric torsion coefficients of the bypass contour. It is shown that the intrinsic twist index generally does not exceed half the linking number of the strip with the polarization singularity lines of the scattered near-field. The twists of the strips are localized near three distinct surfaces, converging on the C-line and usually change their directions. It is shown that the intrinsic twist index is the most suitable for the role of the main topological feature of the optical strip.