We investigate electromagnetic propagation in uniaxial dielectrics with atransversely varying orientation of the optic axis, the latter stayingorthogonal everywhere to the propagation direction. In such a geometry, thefield experiences no refractive index gradients, yet it acquires atransversely-modulated Pancharatnam-Berry phase, that is, a geometric phaseoriginating from a spin-orbit interaction. We show that the periodic evolutionof the geometric phase versus propagation gives rise to alongitudinally-invariant effective potential. In certain configurations, thisgeometric phase can provide transverse confinement and waveguiding. Thetheoretical findings are tested and validated against numerical simulations ofthe complete Maxwell's equations. Our results introduce and illustrate the roleof geometric phases on electromagnetic propagation over distances wellexceeding the diffraction length, paving the way to a whole new family ofguided waves and waveguides which do not rely on refractive index tailoring.
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