Design And Key Technology Research Of Metalens Based On Si/SiO₂ Dielectric Materials

The imaging function of the lens has been recognized and utilized by humans for a long time.Traditional optics mainly realize the imaging or light splitting of the optical target by accumulating the optical path.In order to eliminate phenomena such as aberration and chromatic aberration caused by optical materials,traditional optical systems can only be realized by combining a variety of optical elements.Therefore,the structure of the traditional optical system is relatively complex,and it has many disadvantages such as large volume,large weight,and high cost,which significantly limits its popularization and application in many fields.And miniaturization,lightweight,and low cost are essential future development directions of optical systems.In recent years,with the emergence of three-dimensional artificial composite media based on planar subwavelength structures,metamaterials with subwavelength micro-nano structures have been rapidly developed.They have achieved many extraordinary applications,such as high-dimensional holographic images,beam shaping,invisibility cloaks,polarization control,and absorbers,etc.Metalens is one of the hot research directions.Metalens are based on subwavelength micro-nano structures to control the wavefront of light,and have super-powerful manipulation of light waves,and have the advantages of ultra-light,ultra-thin,and easy integration.In a series of published studies in the visible and near-infrared wavelengths,it was found that metalens can be used in many aspects such as ultra-depth focusing,image differentiation,and high-depth-of-field imaging,which is expected to open a new path for nano-optical imaging and ultra-miniature optoelectronic devices.In this paper,the all-dielectric structure is used to study the optical responses and their corresponding phase modulation in different micro-nano structures based on dielectric materials.Based on the excellent wavefront control capability of the metasurface,the design of the long-wave infrared one-dimensional metalens（cylindrical metalens）and the design of the orthogonal cylindrical metalens,the design of large numerical aperture metalens,the fabrication and testing of metalens,the design and analysis of the ultraviolet projection metalens group and other work research results.The specific research work is as follows:1.Combined with the converging effect of positive cylindrical lens on light,the all-dielectric cylindrical metalens in the long-wave infrared band is studied.Based on the all-dielectric micro-nano structure,a cylindrical metalens with 9μm incident light in the long-wave infrared band is realized.The transmittance of the cylindrical metalens is 78.29%,which breaks through the material limitation of traditional long-wave infrared materials and achieves a high transmittance.On this basis,the focusing effect of the all-dielectric orthogonal doublet cylindrical metalens is analyzed.Within a certain range,the focusing effect achieved by the all-dielectric orthogonal doublet cylindrical metalens is similar to that of a circular metalens.Therefore,we can achieve the focusing effect of conventional convex metalens by designing cylindrical metalens and then performing orthogonal doublet design on them.This break through the material limitations of traditional long-wave infrared materials,and this dramatically reduces the computational design difficulty of ordinary metalens.2.Combining metasurface transmissive metalenses with the requirement for large numerical aperture lenses in optical systems,and based on the all-dielectric micro-nano structure,a metalens for 9μm incident light in the long-wave infrared band is realized,and its focusing effect is analyzed and studied.The metalens can achieve a transmittance of T=55.4%and a numerical aperture of NA=0.983 under long-wave infrared,which breaks through the material limitations of traditional long-wave infrared materials and achieves high transmittance.Meanwhile,through the symmetrical structure of the nanopillars,the designed metalens is polarization-insensitive.Long-wave infrared polarization-insensitive and ultra-large numerical aperture metalens based on all-dielectric metasurfaces have broad application prospects for systems requiring small light interaction or large-angle collection.The long-wave infrared metalens of all-Si dielectric materials was experimentally fabricated and characterized.At the same time,the scanning electron microscope（SEM）and other equipment were used to characterize the structural and optical parameters of metalens array samples.And by building an optical test path,the light spot focused by the metalens was obtained,and the focusing ability of the metalens was experimentally verified.3.In order to solve the problem of the complex structure of the existing traditional ultraviolet system,combined with the metalens design,an integrated ultraviolet all-dielectric metalens group is provided.It designs two metalens subwavelength array groups on two parallel surfaces of the Si O₂ substrate,respectively.And through the optimized design of metalens,the near-perfect beam reduction of parallel ultraviolet light is realized.Under the incident of parallel light,a 4:1 projection imaging was achieved for the mask placed in front of the integrated metalens group.The metalens group has the advantages of ultra-light,ultra-thin,and easy integration,opening a new path for nano-optical imaging and ultra-miniature optoelectronic devices.Compared with the traditional ultraviolet lens group,this design has the advantages of small size,simple system structure,and system stability.