  We resolve the breakdown of angular momentum conservation on two-dimensional
photon tunneling by considering spin Hall effect (SHE) of light. This
interesting effect manifests itself as polarization-dependent transverse shifts
for a classic wave packet tunneling through a prism-air-prism barrier. For a
certain circularly polarized component, the transverse shifts can be modulated
by altering the refractive index gradient associated with the two prisms. We
find that the SHE in conventional beam refraction can be evidently enhanced via
photon tunneling mechanism. The polarization-dependent transverse shift is
governed by the total angular momentum conservation law, while the
polarization-dependent angular shift is governed by the total linear momentum
law. These findings open the possibility for developing new nano-photonic
devices and can be extrapolated to other physical systems.
