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 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.