Tailoring spatially unpolarized light on the Poincaré sphere: From equator states via meridian states to generalized great-circle states

Abstract

In this paper we investigate the generation, manipulation and invariance properties of spatially unpolarized light in the context of classical optics. We generate spatially randomly polarized light by exploiting the optical activity of a so-called Cornu depolarizer and demonstrate tailored, spatial polarization distributions on the Poincaré sphere. We begin with the generation of equator states of spatially unpolarized light, i.e., the manifold of the superposition of all linearly polarized light states in the spatial domain. A quarter-wave plate is utilized to transform these equator polarization states into meridian states and finally a second, subsequent quarter-wave plate results in tilted meridian states or generalized great-circle states on the Poincaré sphere. These results of all realized unpolarized states are visually confirmed by tomographic reconstruction of the spatially distributed polarization states on the Poincaré sphere by extracting the data from the spatially resolved Stokes parameter measurements. Furthermore, all these experimental results are in excellent agreement with classical Mueller formalism calculations based on the Mueller matrices for the Cornu depolarizer and the wave plates, yielding the tailored manifold of polarization states on the Poincaré sphere's surface, confirming the naming of the unpolarized light states in accordance with geodesy. Therefore, we have realized a scheme for the tailored generation of spatially depolarized light based on the Cornu depolarizer and quarter-wave plates with interesting application perspectives and giving further insight into polarization.