  Imbert-Fedorov (IF) shift, which refers to a tiny transverse splitting
induced by spin-orbit interaction at a reflection/refraction interface, is
sensitive to the refractive index of a medium and momentum state of incident
light. Most of studies have focused on the shift for an incident light beam
with a spin angular momentum (SAM) i.e., circular polarization. Compared to
SAM, orbital angular momentum (OAM) has infinite dimensions in theory as a new
degree of freedom of light and plays an important role in light-matter
coupling. We demonstrate experimentally that the relative IF shifts of vortex
beams with large opposite OAMs are highly enhanced in resonant structures when
light refracts through a double-prism structure (DPS), in which the thickness
and temperature of the air gap are precisely sensed via the observed relative
IF shifts. The thickness and temperature sensitivities increase as the absolute
value of opposite OAMs increases. Our results offer a technological and
practical platform for applications in sensing of thickness and temperature,
ingredients of environment gas, spatial displacement, chemical substances and
deformation structure.
