Light Spin Angular Momentum Spatial Mode Converter Based on Dielectric Metasurface

In recent years, the concept of metasurface has brought impact on the way of manipulating light using conventional wavefront shaping components by both reducing the device size and increasing the design flexibility. In this work, a spatial mode converter based on dielectric metasurfaces for spin angular momentum is proposed. The structure parameters of dielectric nanobricks are designed by spatial phase distribution derivation based on the geometric phase and the propagation phase. It is shown that the mode converter can transfer the fundamental spatial mode of spin angular momentum including circular or elliptical polarizations into higher order spatial modes. The generated higher order modes of spin angular momentum contribute a new degree of freedom for light modulation besides the handedness of polarization. The metasurface device can reduce the complexity of the existing mode-division multiplexing systems for spin angular momentum of light, and meanwhile exhibit a high efficiency, which may find applications in optical communication, complex structured beam, and quantum optics.