Large centroid shifts of vortex beams reflected from multi-layers

Abstract

Gaussian beams reflected from a multi-layered dielectric experience a shift in their centroid that is different than that from a single interface. This has been previously investigated for linearly polarized beams and, to a much lesser extent, beams with spin angular momentum. Here a combination of theoretical and computational analysis is used to provide a unified quantification of these shifts in layered dielectrics, for light endowed with an intrinsic orbital angular momentum (OAM) - i.e. vortex beams. Two geometries are considered: air/glass/air and glass/air/glass multi-layers. Destructive interference causes singular lateral shifts in the centroid of the reflected vortex beam for which spin alone produces only a mild modulation. In the case of total internal reflection, both spin and intrinsic OAM contribute to an enhancement of these lateral shifts as the interlayer thickness is decreased. This is just the opposite of the trend associated with longitudinal shifts. We find that vortex beams undergo centroid shifts up to tens of microns, more than an order of magnitude larger than for Gaussian beams.