High-order photonic spin Hall effect and its application in high-contrast imaging

The spin-orbit interaction of light has been extensively examined in reflection and refraction at diverse optical interfaces, which results in the discovery of photonic spin Hall effect (SHE). The fundamental physical essence of this effect is attributed to the one-order effect of polarization rotation associated with one-dimensional geometric phase gradient. Here, we report a unified frame of high-order photonic SHE, which is related to the two-order effect in spin-orbit interaction of light and two-dimensional geometric phase gradient. The conventional one-order photonic SHE is associated with the global transport of the wave vector in momentum space, while the high-order photonic SHE is attributed to the local transport. Direct experimental observation of high-order photonic SHE has been demonstrated in three conventional cases of focusing, diffraction, and scattering. Under the focusing and diffraction conditions, the edge-enhanced images based on the high-order photonic SHE can be realized by inserting two crossed polarizers into a nonparaxial optical system. Under the scattering condition, the confocal imaging system is introduced to observe the high-contrast image and motion trajectory of dynamic transparent particles. We believe that the high-order photonic SHE may develop promising image-processing technique and high-contrast microscopy.