Characteristics of resonance-induced optical vortices and spatial reshaping.

The spatial profile of a beam can experience complicated reshaping after interacting with a planar resonator near resonant conditions. Previously, this phenomenon was recognized as the Goos-Hänchen effect, which only partially explains the experimental observations. In this Letter, we introduce a 2D model that can fully describe the resonance-induced spatial reshaping. The model predicts several general features of the output beam profile and suggests that optical phase or polarization vortices can be generated and manipulated by an arbitrary planar resonator. We validate our theoretical results with experimental measurements using terahertz spectroscopy.