Theoretical Research And Design Of Long Wave Infrared Flat Lens

The research objective of this paper is to design a long-wave infrared plate lens,which works in 8~14?m band,has the advantages of high transmittance,miniaturization,low cost and easy preparation.Currently,there are about three mainstream methods to achieve flat lens: Fresnel lens,graded refractive index lens and metamaterial flat lens.After investigation and analysis,it is found that Fresnel lens and refractive index gradient lens have the shortcomings of low transmittance and difficult preparation,which cannot meet the needs of the project.The metamaterial flat lens relies on the properties of the optical resonator at the sub-wavelength scale,which can theoretically achieve arbitrary control of the wavefront of the incident light,so the lens can be miniaturized and flat.Among them,dielectric metamaterial flat lens has a high transmittance and can be prepared with cheap silicon material in the infrared band of 8~14?m.At the same time,the project can use the relatively mature ICP etching technology.The response of the dielectric metamaterial flat lens to the electromagnetic wave can be obtained by studying its micro-nano structure unit.In this paper,CST software is used to analyze the micro-nano structure unit of dielectric metamaterial flat lens.According to the simulation results,at the center wavelength of 10?m,the bulk silicon structure has a high transmittance,many of them are more than 70%,and the phase control range is more than 300°,which can well meet the project requirements of more than 40% transmittance.On this basis,according to the screening criteria of smooth phase change and small aspect ratio,we get the best data of bulk silicon structure.With the best data of the micro-nano structural unit,this paper presents the design scheme of the dielectric metamaterial flat lens,which divides the lens into the central region and the peripheral region.The central region uses the traditional hyperboloid phase distribution design,and the peripheral region uses the principle of first-order grating to design multiple groups of deflectors.The phase control range of each group of deflectors on the incident light is 0~2?.In this paper,error analysis is also carried out in the design scheme,which proves that the error can be ignored when the data in the database is accurate enough and the number of columns in the circular direction is large enough.Finally,the design parameters of the dielectric metamaterial flat lens are given.Theoretically,the transmittance of the lens at the center wavelength of 10?m is more than 70%.The innovation of dielectric metamaterial flat lens studied in this paper is that although previous studies have been done in visible light,terahertz and near infrared band,the research on dielectric metamaterial plate lens with band of 8~14?m is still a new field.