Artificial topological charge designed by azimuthal metagratings can be used to control sound vortex diffraction.

We report experimental and theoretical studies of nonvolatile photorefractive holographic recording in ${\mathrm{LiNbO}}_3:\mathrm{Cu}:\mathrm{Ce}$ crystals with two illumination schemes: (1) UV light for sensitization and a red interfering pattern for recording and (2) blue light for sensitization and a red pattern for recording. The results show that the oxidized ${\mathrm{LiNbO}}_3:\mathrm{Cu}:\mathrm{Ce}$ crystals can provide high, persistent refractive-index modulation with weak light-induced scattering. The optimal working conditions and the prescription for doping and oxidation–reduction processing that yields the maximum refractive-index modulation are discussed.

We proposed and demonstrated that PT symmetric metamaterials could be used to achieve enhanced spin Hall effect (SHE) of light. We find that when laser mode is excited in PT symmetric system, the enhanced SHE could be obtained in both transmitted and reflected beams. In addition, as exceptional points (EPs) of PT symmetric system can happen for both p- and s-polarizations, the enhanced SHE of reflected light can function for both horizontally and vertically polarized incident beams. Particularly, these EPs can lead to unidirectional reflectionlessness, asymmetric SHE with maximum contrast ratio of 48 is obtained by launching light beams near EPs. Our work opens up a new path to obtain enhanced transverse displacement for both reflected and transmitted light and enables more opportunities in manipulating photonic SHE.