When a beam is reflected (or refracted) at optical interface or propagating through an inhomogeneous medium, photons with opposite spin angular momenta will separate with each other, resulting in a spin-dependent splitting of light, and this phenomenon is called the photonic spin Hall effect (SHE). The photonic SHE is a fundamental physical effect that originates from the spin-orbit interaction of light. It can be regarded as an analog of the spin Hall effect in electronic systems: the right-handed and left-handed circular polarization components of light play the role of spin-up and spin-down electrons, respectively, and the refractive index gradient plays the role of the potential gradient. The unique physical properties of photonic SHE and its powerful ability to manipulate photons have made it a hot spot in modern optics, with wide application prospects in precise metrology, analog optical processing, quantum imaging, and microscopy imaging. Recently, the research group of Professors Hailu Luo/ Shuangchun Wen from Hunan University in China has been invited to review the fundamentals and emergent applications of photonic SHE. From the perspective of spin-orbit interaction underpinned by geometric phases, they described the fundamental concepts and recent advances of photonic SHE systematically, and highlighted its important applications in physical parameter measurement, analog optical computing, and all-optical image edge detection.
