Research On Broadband Focusing Theory And Simulation Of Planar Metalens

Traditional optical systems still have many problems in practical use,such as large volume and high production cost.For example,for the prime lens of SLR camera,a complex lens group is designed in order to obtain excellent performance,which requires not only a single lens,but also the combination of lenses with high precision,which increases its manufacturing cost.As a new type of optical device based on metamaterials(metasurface),metalens has the characteristics of large-scale integration,miniaturization and diversified functions compared with traditional lens.This provides great flexibility for optical system design and makes it one of the research hotspots at the present stage.In this thesis,according to the phase control theory of the metalens in the visible light band(400-800nm),the influence law of the structure of the metalens element on its optical properties under several typical wavelengths is designed and studied by using the finitedifference time-domain method.After building the unit database,using Matlab program control modeling software East FDTD,the units are arranged on the plane lens,and the metalens which can realize wide-band and low dispersion focusing is designed.Firstly,in theory,the phase of incident light is modulated by the metalens,so that the wave front of incident light changes to achieve the focusing effect.The phase modulation is realized by the element structure distributed on the surface of the metalens.Therefore,in the first step,the principle of phase regulation is derived from the Jones matrix expression of the structure of the incident light irradiation unit.In the second step,according to the feasibility of phase regulation,the principle of shaping the incident light wave front by metalens is given based on the Huygens-Fresnel principle.According to the theoretical support,this thesis designs the unit structure which can realize the phase control through a lot of simulation.We used MATLAB programming control modeling software EASTFDTD to arrange the unit structure reasonably to form the metasurface.We covered the metasurface with a plane lens to form a metalens.The simulation results of the metalens show that the metalens designed in this thesis can achieve low dispersion focusing in the visible light band(400-800nm).For the problem that the focusing power of the long wavelength part is low,this thesis discusses the follow-up research methods.Finally,the shortcomings and problems of this thesis are summarized,and the solutions and future research directions are given.