In view of wide applications of vector beams and powerful light manipulation ability of metasurfaces, this paper studies the generation of two kinds of vector beams with different polarization singularities based on metasurfaces. One kind of vector beams are the linearly polarized vector beam (LPVB) with uncertain polarization orientation and the other kind of vector beams are the elliptically polarized vector beam (EPVB) with hybrid polarization states with uncertain polarization orientation, ellipticity and handedness. These vector beams can be decomposed into two or more uniform polarization states carrying the spiral phases. The metasurfaces consisting of rotated cross nanoholes are designed to generate vector beams on basis of the decomposition of vector beams and phase modulation of nanoholes. The simulation results verify the availability of the designed metasurfaces and the experiment results validate the generation of two kinds of vector beams. The generation of complex vector beams based on compact metasurfaces can bring more application possibilities of vector beams in classical physics and quantum sciences.

Highly customized and miniaturized structured light is expected in many application fields. A kind of structured vortex generators is proposed based on a metasurface consisting of rectangular nanoholes etched in a silver film, and the generated vortices with the same or different topological charges are distributed along the radial direction. The geometric metasurface is completed with the help of optical holography technology, and the structured vortex generator possesses high working efficiency and large information capacity. The proposed vortex generators work under circularly polarized light illumination, and the reproduced vortices of multiplexing vortex generator depend on the handedness of the circularly polarized light. This work paves a way to generate new structured light fields. The radially distributed vortices may be utilized to simultaneously screen or separate microparticles. The compact design of the structured vortex generator and the convenient switch of different structured vortices will be a benefit to expand the applications of structured vortex fields.

Singular optics is a branch of modern optics, and it usually refers to various singularities including phase, polarization, and energy flux singularities. Lots of excellent researches in foundation and application fields relate to optical singularities. Nanotechnology enables the manipulation of optical singularities in nanometer scale. Metasurfaces consisting of nanoscatterers have aroused intensive interest in recent years because of the ultrathin structure and the powerful light manipulation ability. Optical singular fields generated by metasurfaces built on tiny holes attract much attention. The recent research progress about the optical singular fields in nanoscale is provided here and the physical mechanism of the formation of optical singularities including phase singularity, polarization singularity, and hybrid singularity are discovered in terms of tiny holes. The beneficial reference is provided here to investigate the related works, and the applications of optical singularities in nanometer scale are promoted.

In view of wide applications of vector light with a non-uniform polarization state, a compound vector light generator is proposed to generate compound vector light. One compound vector light contains two or more non-uniform polarization modes and several annular intensities, which can carry more polarization information and possess higher dimensional singularity. The proposed compound vector light generator consists of cross nanoholes with high polarization conversion efficiency; it works under linear polarized light, and the mode of the generated compound vector light can be adjusted through rotating cross nanoholes. The structure parameters of the compound vector light generator are optimized with the aid of numerical simulation, and the simulation results for the generated light fields verify the performance of the proposed device. The advancement of the compound vector light and metasurface design of the compound vector light generator can assist in the exploration of novel singular properties of light fields and the broadening of applications of vector light fields.

The phase delays introduced by anisotropic nanounits include propagation phase delay, resonant phase delay and geometric phase delay. Various phase devices can be formed based on the metasurfaces consisting of anisotropic nanounits and the phase devices of the same kind function have different performances because of different working modes. In this paper, metalenses and vortex metalenses are chosen as examples to compare the optical performance of metasurface phase devices based on three kinds of phase compensation techniques. We design separately three kinds of metalenses and vortex metalenses using the cross nanoholes, L-shaped nanohole and V-shaped nanoholes and simulate numerically their intensity and phase distributions. Additionally, the results show the differences among these elements in structure complexity, polarization dependence, working efficiency and phase uniformity. The comparison for three kinds of metalenses clearly shows the merits of different phase compensation techniques and this work must be helpful for expanding the practical applications of metasurfaces.