Modulation of spin-dependent diffraction based on dielectric metasurfaces

We propose theoretically and realize experimentally a tunable single-slit diffraction based on dielectric metasurfaces. Our dielectric metasurfaces can be regarded as polarization converters to generate inhomogeneous polarized light periodically variant in x direction. Different from the well-known single-slit diffraction of the scalar light field, our diffraction patterns exhibit two columns of diffraction fringes, which conceals spin-dependent splitting phenomenon. The underlying mechanism is attributed to the inherent nature of the Pancharatnam-Berry phase in the inhomogeneous polarized light. Interestingly, the spin-dependent splitting can be enhanced by increasing the polarization rotation rate of the inhomogeneous polarized beam or the transmission distance. Further, tunable diffraction phenomenon is observed with different slit widths or variant rotation angles of the dielectric metasurface and the slit. Our results may offer potential applications in spin-controlled nanophotonics.