Design And Research Of Optical Devices Based On All Dielectric Metasurface

Metasurface is a two-dimensional representation of metamaterials with ultrathin properties,which can effectively control the phase,amplitude and polarization of light in transmission or reflection modes.With the development trend of miniaturization and integration of optical system,due to the disadvantages of traditional optical elements such as large volume,high cost and complex process,metasurface elements are expected to replace traditional optical elements with their ultra-thin characteristics.Among them,all-dielectric metasurface has high transmission efficiency and is mostly composed of semiconductor materials,so this metasurface has great potential in practical production and application.In recent years,most of the metasurface designs are based on geometric phase.Phase modulation of circularly polarized light is carried out by adjusting the rotation Angle of the structural elements on the metasurface.However,the energy of light will be lost to some extent in the process of obtaining circularly polarized light.Based on the nanometer element of transmission phase,a group of all-dielectric metasurface devices composed of nonmetallic materials are designed in this paper,which are mainly used to realize the deflection of line-polarized light and the focusing of non-polarized light.The simulation results show that the nanometer element based on transmission phase can phase modulate the transmitted light.The specific work includes:(1)Based on the material parameters of silicon and silicon dioxide,a structural unit was designed to place the silicon nano-column on the silicon dioxide substrate.The FDTD method was used to simulate the structural unit,and the changes of phase and transmittance with the radius of the nano-column under the working wavelength were obtained.Based on the simulation results,two kinds of high efficiency transmission wavefront control devices are designed,which are anomalous beam deflector and polarization-insensitive metalens respectively.The performance of these two devices is studied by theoretical analysis and numerical simulation.(2)Using the generalized,nie er law of refraction,design of abnormal refraction of light beam deflector can make vertical basal deflect incoming light,based on the structure of 12 units of deflector as an example for the design and optimization,the theoretical calculation of the deflection Angle is 12.1°,the optimized one-dimensional beam deflector is out of beam deflection 12.02°,high transmission efficiency,can reach 80%.A two-dimensional beam deflector is designed by using the optimized structure unit.The deflection effect is ideal.The results show that the beam deflector based on phase transfer metasurface design can make the line-polarized light deflector.(3)Based on silicon nanopillar,polarization insensitive metalens with different focal lengths are designed.The size is 30.5?m*30.5?m,which is composed of 2500 structural units.When the focal lengths of the lenses are 77.276?m and 37.4755?m,the diffraction limits are 4.79138?m and 2.46635?m,respectively.The FWHM of the horizontal profile of the focusing spot is 4.8102?m and 2.5021?m,respectively.The two metalens can achieve almost diffraction limited focus.It shows that the phase modulation capability of the metalens based on the phase transfer metasurface design can make the non-polarized light produce almost the same focusing effect as the diffraction limit.In conclusion,based on the transmission phase all-dielectric metasurface,this paper conducts an in-depth study on the performance of beam deflectors and metalens.These devices have great application potential in infrared imaging,miniaturized photoelectric systems and other fields,and play a positive role in the development and application of all-dielectric metasurface optical devices.