Design And Applied Research Of Dielectric-based Metasurfaces

With the development of the micro-nano processing technology and the research on electro-magnetic waves,we could take advantage of the micro-nano structures to control the behavior of the electromagnetic waves,and realizing special phenomenon and applications which couldn't happen with natural materials.This kind of materials which composed of nanostructures are called metamaterials.As one of the important branch of the metamaterials,metasurface is the two-dimensional realization form of the metamaterials.It has a series of advantages such as low dissipation,easy for fabrication,etc.There are many applications based on the metasurface,in-cluding electromagnetic invisibility cloaking,abnormal refraction of light,the metasurface holo-gram,planar lenses,etc.In this thesis,we studied the dielectric-based metasurfaces in the aspect of electromagnetic waves control.Mainly including the design of the splitting device producing two orthogonally circularly polarized light with one linear polarized incident light,metasurface lenses,modulation of far-infrared light transmission by graphene-silicon surface structure,etc.Firstly,we realized the photonic spin Hall effect using transmission-type metasurface in the near infrared.We studied the beam-splitting metasurface device using coordinate transformation method with the Jones matrix,and get two kinds of implementations.By introducing the back-ground phase gradient,we will also gave a deflection angle to all the output circular polarized light.So we could get the asymmetrical photonic spin Hall effect.We designed the structure of the metasurface based on the calculation results,and verify the design with the simulation results.Inspired by the coding metasurface,we design the tunable metasurface structure,which could be modulated by changing the polarization direction of the incident light to change the direction of outward circularly polarized light.Secondly,We extended the application range of holographic Gerchberg-Saxton(G-S)iterative algorithm.We studied the metasurfaces in the application of the hologram.At present,widely used method of computing hologram is G-S algorithm.It could get the holographic phase distribution by iterative optimization between the hologram plane and the target image plane using Fresnel diffraction algorithm.Based on this method,we set two target image planes,and optimize among two target image planes and one hologram plane,finally,we got the holographic phase distribution which could present different graphic information at different position with parallel incident light.We verified the design by Matlab calculation results.Then,we discussed the advantages of artificial electromagnetic surface lens to Fresnel lens and designed a single metasurface lens working in multi-wavelengths.We compared the meta-surface with the traditional Fresnel lenses.We found that the chromatic dispersion are the same between the two kinds of lenses.They are all based on the grating type.But the metasurface lenses is better in focal efficiency and diffraction inhibition in high numerical aperture(NA)than the Fres-nel lenses.In view of the present question of lens dispersion,we designed the mechanically robust metasurface lenses for RGB colors and avoid the interference problem between different channels by setting the filters on the metasurface lenses.The focusing effect was verified through the sim-ulation.Because of the characteristics of ultra-thin and ultra-light,metasurfaces are very suitable for applications in aerospace,missile guidance,which has special requirements on the mass and the volume of the lenses.For the tunable surface,we tried to take advantage of the Schottky junction between graphene and silicon material to modulate the transmission of infrared incident light.The experiments show that the bias voltage and pump light can change the infrared incident light transmittance value.This kind of modulation method has potential applications for the future tunable metasurfaces.Finally,we summary the thesis and give some prospects about future dielectric-based meta-surfaces.