  In magnetic materials, skyrmions are nanoscale regions where the orientation
of electron spin changes in a vortex-type manner. Here we show that spin-orbit
coupling in a focused vector beam results in a skyrmion-like photonic spin
distribution of the excited waveguided fields. While diffraction limits the
spatial size of intensity distributions, the direction of the field, defining
photonic spin, is not subject to this limitation. We demonstrate that the
skyrmion spin structure varies on the deep-subwavelength scales down to 1/60 of
light wavelength, which corresponds to about 10 nanometre lengthscale. The
application of photonic skyrmions may range from high-resolution imaging and
precision metrology to quantum technologies and data storage where the spin
structure of the field, not its intensity, can be applied to achieve
deep-subwavelength optical patterns.
