On anomalous optical beam shifts at near-normal incidence

We develop the theory of optical beam shifts (both Goos–Hänchen and Imbert–Fedorov) for case near-normal incidence, when incident angle becomes comparable with angular divergence. The developed uncovers unified origin anomalous shift enhancement via geometric Berry phase singularity. Particularly, we predict large occurring small incidence angles. also propose a simple experimental scheme involving quarter-wave q-plate that allows us to observe giant transverse longitudinal, spatial simultaneously. Finally, analyze relevant parameters, polarization structure, intensity profiles shifted transmitted beam. Our results can find applications in spin–orbit photonics, optics, sensing applications, quantum weak measurements.