Arumugam, Stree VithyaStree VithyaArumugamJisha, Chandroth P.Chandroth P.JishaMarrucci, LorenzoLorenzoMarrucciAlberucci, AlessandroAlessandroAlberucciNolte, StefanStefanNolte2024-03-212024-03-212023https://publica.fraunhofer.de/handle/publica/46434710.1364/OE.5055382-s2.0-8518013107338178503A circularly polarized (CP) beam propagating in a rotated anisotropic material acquires an additional phase delay proportional to the local rotation angle. This phase delay is a particular kind of geometric phase, the Pancharatnam-Berry phase (PBP), stemming from the path of the beam polarization on the Poincaré sphere. A transverse gradient in the geometric phase can thus be imparted by inhomogeneous rotation of the material, with no transverse gradient in the dynamic phase. A waveguide based upon this principle can be induced when the gradient accumulates in propagation, the latter requiring a longitudinal rotation in the optic axis synchronized with the natural rotation of the light polarization. Here, we evaluate numerically and theoretically the robustness of PBP-based waveguides, in the presence of a mismatch between the birefringence length and the external modulation. We find that the mismatch affects mainly the polarization of the quasi-mode, while the confinement is only slightly perturbed.enjournal article