Enhanced opposite Imbert–Fedorov shifts of vortex beams for precise sensing of temperature and thickness

Abstract

The 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 studies have focused on the shift for an incident light beam with a spin angular momentum (SAM), i.e., circular polarization. We demonstrate experimentally that the relative IF shifts of vortex beams with large opposite orbital angular momentums (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.