occurring materials, it is difficult to further reduce the thickness of optical elements based on such a design theory. [1] Metamaterials are artificially structured materials which attain their properties from the unit structures rather than the constituent materials, [2] so their optical properties such as the effective electric permittivity and the magnetic permeability can be tuned accordingly. [3] To overcome the fabrication difficulties of metamaterials working in the optical range, a 2D metamaterial, or metasurface has been developed, which consists of a layer of optical antennas to locally modify the phase, amplitude, and polarization of the scattered light. [1b,4] Optical antennas are typically made of metals or high refractive index dielectrics, which can be fabricated through standard nanofabrication process, such as electron beam lithography, liftoff process, focused ion beam milling, or reactive ion etching, thus the complexity of the fabrication is greatly reduced in comparison with that for their 3D counterparts. Besides, metasurfaces can change the properties of the scattered light by using antennas with a dimension smaller than the operating wavelength, which exhibits high resolution and can avoid the higher diffraction orders of the traditional diffractive optical devices. In addition, the thickness of the metasurface is much smaller than the incident wavelength which makes them practical for device miniaturization and system integration.Metasurfaces are generally divided into two categories based on their mechanisms: [1a] the one based on the dispersion of antenna resonance and the one based on the Pancharatnam-Berry phase, namely, geometric phase. [5] The former relies on the delicate design of antenna geometry to obtain the desired phase delay of the scattered light. For example, the V-shaped antennas with various arm lengths and opening angles can provide phase gradient to the cross-polarized light, which verifies the generalized laws of reflection and refraction. [6] In contrast, the latter usually contains antennas with the same structure but spatially variant orientations. [7] Each antenna can be regarded as an anisotropic scatterer, which converts part of the incident circularly polarized (CP) light to its opposite helicity with a geometric phase ± 2ψ. The symbol ψ represents the orientation angle of the antenna, with + sign for the conversion from left-handed circularly polarized (LCP) light to righthanded circularly polarized (RCP) light, and the − sign for RCP to LCP light. Thus, a sampled phase function can be imparted to the scattered light from an array of antennas with designed Metasurfaces, planar metamaterials consisting of a single layer or several layers of artificial structures, not only form the basis for fundamental physics research but also have considerable technological significance. Metasurfaces can locally modify the optical property within a subwavelength range, which can facilitate device miniaturization and system integration. Metasurfaces have shown extraordin...