  The formation of a superstructure - with a related Moir\'e pattern - plays a
crucial role in the extraordinary optical and electronic properties of twisted
bilayer graphene, including the recently observed unconventional
superconductivity. Here we put forward a novel, interdisciplinary approach to
determine the Moir\'e angle in twisted bilayer graphene based on the photonic
spin Hall effect. We show that the photonic spin Hall effect exhibits clear
fingerprints of the underlying Moir\'e pattern, and the associated light beam
shifts are well beyond current experimental sensitivities in the near-infrared
and visible ranges. By discovering the dependence of the frequency position of
the maximal photonic spin Hall effect shift on the Moir\'e angle, we argue that
the latter could be unequivocally accessed via all-optical far-field
measurements. We also disclose that, when combined with the Goos-H\"anchen
effect, the spin Hall effect of light enables the complete determination of the
electronic conductivity of the bilayer. Altogether our findings demonstrate
that sub-wavelength spin-orbit interactions of light provide a unprecedented
toolset for investigating optoelectronic properties of multilayer
two-dimensional van der Waals materials.
