Study On The Dielectric Metalens In Optical Band

The rapid development of information technology has made the world change rapidly.The crystallization of human wisdom has penetrated into all aspects of production and life,and various types of optoelectronic information equipment are gradually becoming miniaturized and integrated.For optical devices,from the original huge and cumbersome to the continuous breakthrough of traditional processes and physical limits,some artificially designed nano-sub-wavelength microstructure—metasurface that surpass the properties of natural materials have emerged as the times require.Metasurface,to some extent,can be called a two-dimensional form of metamaterial.With its unique advantages,it has become a hot topic in related research fields.The traditional uniform dielectric lens usually uses its special spherical structure to control the emitted electromagnetic waves.The metalens skillfully combines the advantages of the metasurface structure with the lens,which makes the lens research enter a new stage.Compared with metal antenna metalens,dielectric metasurface lenses has better optical characteristics and smaller ohmic loss in the optical band,so it is more superior.In this paper,on the premise of circularly polarized optics,based on different materials and different shapes of nano-antenna structures,dielectric metasurface lenses with different optical bands and different application scenarios are designed.The specific research contents are as follows:1.A transmissive all-dielectric metalens which works in the near infrared band and adjusts the phase through the height change is designed by using the rectangular silicon nano antennas.Based on the resonance phase theory,the geometric parameters of the silicon nano-antenna are changed,and the effective focusing of the rectangular silicon nano-antenna metasurface lens structure is achieved at an incident wavelength of 950 nm.After verification,the focal length of this structure is basically unchanged in the near-infrared band of 950nm?1100nm,and the broadband achromatic effect in a certain band range is achieved,and its transmission efficiency can reach 68%.In addition,by adjusting the size of the lens,the influence of the change of its numerical aperture on the focusing performance of the lens structure is studied.Finally,a bifocal lens structure is designed using a lens array,which provides a reference for the design of a multifocal metasurface lens.2.Using Ga P(gallium phosphide)elliptical cylindrical nano-antenna,based on the Pancharatnam-Berry phase principle,this paper designs anomalous refraction metasurface and high transmission efficiency metalens working in the visible light band.Utilizing the anisotropy of the elliptical cylinder nano-antenna structure,the nano-unit structure is rotated at different angle to change the polarization state of the incident electromagnetic wave to adjust the phase.When the left-handed circularly polarized light with a wavelength of 650 nm is used as the incident electromagnetic wave to be incident perpendicularly,both of the designed anomalous refraction metasurfaces can achieve angular deflection that are basically consistent with the original theoretical angles.At the same time,the focusing performance of the focusing metasurface lens structure designed at the resonance wavelength is good.The simulation results show that the transmission efficiency of the metasurface structure composed of this nano-antenna unit can reach about 96%.