Nondiffracting polarization textures enabled by anisotropic loss.

Overcoming diffraction spreading is a crucial challenge in wave physics. We report a mechanism for suppressing diffraction of skyrmionic polarization textures by leveraging anisotropic absorption in inhomogeneous media. We show that dichroic media with a longitudinally varying degree of dichroism can compensate the diffraction spreading of the skyrmion tube, enabling the formation of non-diffracting Stokes skyrmions. In contrast to trapped waves in gradient-index media, we present a non-diffraction mechanism in media with uniform refractive index in the transversal direction, thus the finite-size vortex beams themselves experience diffraction, but their combined polarization texture remains confined within a non-spreading tube. We also show the robustness of the non-diffraction mechanism under changes in the input beam size and under beam shifts along longitudinal and transversal directions.