Observation of the non-diffraction of natural skyrmions with subwavelength confinement around optical vortices

It is a fundamental fact of waves that they spread as they evolve freely, regardless of their nature. Previous research to overcome diffraction spreading has led to idealized waves that, in real settings, exhibit quasi-non-diffraction and eventually spread. Here we demonstrate that the optical skyrmion that is naturally present in optical vortices is a structure of light that is exempt from diffraction. It propagates without any change in shape and size within a tube of arbitrary subwavelength radius determined by the vortex orbital and spin angular momenta. Non-diffracting propagation of a subwavelength structure of light that does not raise infinite-power issues differs drastically from all previous forms of light propagation, which may open up new perspectives in its countless applications.