  We theorize the spin Hall effect of light (SHEL) on a nano-metal film and
demonstrate it experimentally via weak measurements. A general propagation
model to describe the relationship between the spin-orbit coupling and the
thickness of the metal film is established. It is revealed that the spin-orbit
coupling in the SHEL can be effectively modulated by adjusting the thickness of
the metal film, and the transverse displacement is sensitive to the thickness
of metal film in certain range for horizontal polarization light. Importantly,
a large negative transverse shift can be observed as a consequence of the
combined contribution of the ratio and the phase difference of Fresnel
coefficients.
