Propagation of optical vector and scalar vortices in an atomic medium with closed-loop tripod configuration

We investigate the propagation of an optical vector vortex beam in an atomic medium featuring four-level tripod transitions, where ground-state coherence is mediated by a transverse magnetic field. The vector beam consists of left- and right-circularly polarized components, each carrying an optical vortex with opposite orbital angular momentum (OAM). We study the linear response of the medium to the vector beam in order to determine the evolution of the beam's intensity and polarization profile. We find that the beam structure undergoes significant transformations as it propagates: the transverse intensity evolves from a ring-shaped profile to a petal-like structure, while the polarization transitions between left-circular, linear, and right-circular polarizations. Furthermore, when only the right-circular polarization component (a scalar vortex) enters the medium, it parametrically generates a left-circular polarization component, transferring its OAM to the generated field. This process converts the initial vortex beam into a superposition of left- and right-circular components, forming a scalar vortex beam where both polarization components carry the same OAM.