Optical metasurfaces are two dimension form of metamaterials composed of metal or dielectric subwavelength resonators. These ultra-thin flat surfaces could manipulate the wavefront by local controlling of the phase, amplitude and polarization with subwavelength spatial resolution.
Nowadays, unlike the metallic metasurfaces, the dielectric counterparts have been gained remarkable attention due to their low loss nature at the visible and infrared frequencies. The flat nature of high efficient metasurface opens up new possibilities for integration of optical chips. Therefore, many optical devices such as lenses, holographic systems, beam deflectors and vortex beam generators have been introduced and fabricated.
It has been demonstrated that Silicon metaatoms as a constitutional element enhance the efficiency of metasurface at telecommunication wavelength and can also be fabricated in one lithographic step. In addition, it is appreciably compatible with the complementary metal oxide semiconductor (CMOS). The main challenge of designing high-performance metasurface for any application is providing $2\pi$ phase shifts by means of metaatoms. Silicon with high refractive index could support different order of electric and magnetic Mie-type resonances in the optical spectral range. The spectral position of these localized resonances could be tuned by adjustment of resonator geometrical dimensions. Even more importantly, Kerker condition between the first order of electric and magnetic resonances could be achieved. The overlapping of resonance modes results to $2\pi$ phase shift together with near unit amplitude of transmitted wave through metaatom.