New paper in Journal of Optics with a generalization of the degree of polarization concept to other Poincaré spheres
Our last paper published in Journal of Optics is entitled Extending the degree of polarization concept to higher-order and orbital angular momentum Poincaré spheres.
In this work, done in collaboration with Dr. Carlos Hernández-GarcÃa, from University of Salamanca, we apply the density matrix formalism that describes any standard polarization state (fully or partially polarized) to describe vector beams and spatial modes with orbital angular momentum (OAM). We provide a comprehensive description of the mapping between the corresponding Poincaré spheres (PSs); namely: the polarization PS, the higher-order PS (HOPS) and the orbital angular momentum PS (OAMPS).
Whereas previous works focus on states located on the surface of these spheres, here we study vector and scalar modes lying inside the corresponding PS. We show that they can be obtained as the incoherent superposition of two orthogonal vector (or scalar) modes lying on the corresponding sphere surface. The degree of polarization (DoP) of a classical polarization state is thus extended to vector beams and OAM modes.
We used a q-plate to experimentally map any state in the polarization PS onto the HOPS, and a linear polarizer to finally project onto the OAMPS. We design a new polarization state generator, based on two geometric phase gratings and a randomly polarized laser, which generates partially polarized light in an efficient and controlled way.