SU(2) polarization evolution on higher-order Poincar\'e sphere by using general $q$-plate

Abstract

This paper investigates the rotational dynamics on the higher-order Poincar\'e sphere with the use of $q$-plate by exploring three key aspects: the topological condition, the global-local rotation, and the SU(2) polarization evolution on the sphere. The polarized light beam corresponding to this sphere and $q$-plates shares analogous topological features, characterized by azimuthal variation. We have formulated the topological condition that establishes a connection between the $q$-plate and the higher-order Poincar\'e sphere, enabling the SU(2) polarization evolution on the same higher-order Poincar\'e sphere. Leveraging this correspondence, we have shown that a single \textit{global} SO(3) rotation on the higher-order Poincar\'e sphere is a collection of multiple \textit{local} SO(3) rotations on the standard Poincar\'e sphere. SO(3) is related to SU(2) through a two-to-one surjective homomorphism, with SU(2) serving as its double cover. Moreover, we demonstrate that a general $q$-plate, defined by a continuously tunable retardance ranging from $0$ to $2\pi$ and an offset angle ranging from $0$ to $\pi/2$, provides the complete coverage on the higher-order Poincar\'e sphere.