Design And Research Of All-dielectric Metasurface Applied To Wavefront Control

Conventional optical components,such as lenses,waveplates and polarizers,have been widely developed and used in many electronic and optical devices.However these components are bulky,they are not suitable for miniaturization and integration.Thereby,making the material lighter and thinner becomes the researcher’s design goal.The metasurface is a new kind of metamaterial.It is suitable for ultra-thin,ultra-light design purposes due to the sub-wavelength thickness,and has received wide attention form researchers once it has been proposed.Although plasmonic metasurfaces have unique advantages in controlling electromagnetic waves,their high absorption and ohmic loss is problematic in transmission at optical frequencies.The dielectric metasurfaces can show the high transmission efficiency because they do not suffer from the intrinsic nonradiative losses in metals.Based on this background,this paper studied the manipulation of optical wave by all dielectric metasurfaces,the main contents are illustrated as follows:1)The generalized Snell’s law is derived based on Fermat’s law and phase gradient.The all-dielectric gradient metasurface is designed.We calculate the diffraction efficiencies of all diffracted angle using FEM simulation,the result shows that the most optical power is concentrated on 1th diffraction beam,which confirms the generalized Snell’s law.2)The basic working principle of metalens is introduced and all-dielectric metalenses with numerical apertures of 0.22 and 0.91 are designed.The fullwidth at half-maximum(FWHM)of the focused line for these two metalenses are very close to the theoretical diffraction-limited values,which show the high imaging resolution of the metalenses we designed.Moreover,the subwavelength resolution imaging can be obtained by the metalens with the numerical aperture of 0.91.3)We show that a simple single-layer dielectric gradient metasurface enables high-efficiency asymmetric optical transmission under the oblique incidence.The underlying mechanism is ascribed to the unbalanced excitation of surface evanescent waves for forward and backward light.Compared with other multilayer structures for asymmetric transmission,the structure we designed is simple and easy to construct.