Research On The Design And Optical Properties Of Artificial Microstructure Material Flat Lens

With the development of human civilization and the advancement of science,the demand for portable or wearable optical equipment or system with lightweight and excellent performance is increasing,which greatly improves the requirements for optical planar elements.However,planar elements based on diffractive optics and thin-film optics have limited functions and difficult to integrate,which are difficult to meet application requirements.The flat lens of artificial microstructure material has become a hot spot in the research of micro-nano-optics because of its characteristics of controlling beam transmission in micro-nano size.At present,the artificial microstructure material flat lens mainly revolves around focusing or imaging quality optimization,its size or performance is often difficult to meet the non-destructive testing,complex lightwave regulation,and other applications.Aiming at the application requirement of the flat lens and the contradictions of the current flat lens and the current difficulties in the application of special fields such as non-destructive testing,the design and optical characteristics of artificial microstructure material flat lens are studied.The main work of this thesis is as follows:1.A large object distance super-resolution flat lens is designed and its imaging characteristics are studied.Firstly,the imaging of the gradient equivalent medium(GEM)flat lens is studied by negative refractive theory,and the results show that the GEM flat lens can break through the object distance limit.Then,based on the analysis of GEM imaging characteristics,we designed a gradient photonic crystal(GPC)flat lens by the theory of equal-frequency surface.The GPC flat lens can break the diffraction limit and realize superresolution imaging in the range of 2d to 5d,and its imaging resolution can reach up to 0.4? at the maximum object distance of 5d.Also,the flat lens has the characteristics of the image spot size(full width at half maximum)does not increase with the increase of object distance and can realize off-axis point source imaging with large object distance.The results of this study can provide a valuable reference for the construction of large-scale,small-size flat lenses,and have important application prospects in optical integrated devices.2.Based on generalized Snells law,a dual-layer metasurfaces lens is designed.By making phase delays of two metasurfaces interacted with each other,it can realize optical asymmetric transmission and focusing simultaneously.Considering the drawbacks of the middle region of metasurface on the right side cannot be involved in focusing,the low composition of the light waves involved in the focus,as well as the sidelobe of optical asymmetric focusing is large,the design theory of asymmetric focusing lens(AFL)is optimized further.The optimized metasurfaces lens can realize the near-zero-sidelobe(NZS)asymmetric focusing on the subwavelength scale.Moreover,this feature is valid in the wideband range.The research results have great application potentials in optical micronano processing,quantum communication,optical micromanipulation,and microscopic imaging.