Study On Mid-infrared Planar Superlens And Its Optical Manipulation Characteristics

Since the discovery infrared radiation by Herschel in 1800,the infrared technology has developed more than a century,which has been widely used in space communications,military navigation,infrared thermal imaging,infrared remote sensing and many other fields.Compared with the traditional infrared optical components,the planar super-lens developed based on the mid-infrared band has many advantages,such as high degree of freedom of regulation,good industrial compatibility,high efficiency,conformal design of the surface,and easy integration.Due to theoretical innovation,planar superlens technology has greatly extend the design of novel optical devices,which breaks through the technical bottleneck of optical devices toward micro-integration,array and lightweight development.All the research has become a hotspot in recent years.In this paper,based on waveguide theory,effective medium theory,generalized snell's law and other theories,we designed a two-dimensional plane lens with high focusing efficiency,good achromatic performance in mid-infrared(3-5 ?m)range.In addition,we tried our best to optimize the optical performance of planar super lens,by using finite different time domain(FDTD)simulation method.We carried out a series of research work optimize the demand structure of the lens with a goal of high-efficiency focusing,super-resolution imaging,and good achromatic performance.The specific research content of this paper is as follows:First,a metasurface element structure with strong resonance in the mid-infrared band is designed.By using FDTD simulation method,the polarization state,amplitude and intensity of scattered light with different responses under different structural parameters were obtained.All the structures were composed of the silicon and calcium fluoride.Based on the P-B phase theory and Huygens principle,a variety of different numerical apertures and arrangements were designed for far-field planar super-lenses in different scenes.Second,the research on planar super-lens design and its focusing efficiency and super-resolution performance.In order to improve the focusing efficiency of the planar super-lens in mid-infrared,this paper designs a metal-insulator-metal(MIM)subwavelength resonant structure based on the principle of FP resonance(FPR)enhancement of the plane super-lens.By changing the structural parameters of the "brick"unit and the thickness between the two metal layers,the unit structure can also reach a resonance enhancement effect via adjusting the phase response.Through calculation experiments,it is found that the focal spot intensity of the concentrated beam center obtained by this method is increased 1.5 times larger than that of original basis.Then,A design method of a multi-wavelength achromatic lens is proposed.By using the wavelength selectivity of the sub-wavelength element structure and the wide-band response characteristics of the P-B phase,the amplitude modulation is separated from the phase modulation,and the sub-wavelength structure with different wavelength responses is reasonably arranged,and the design is implemented on 3.2m,4.1?m and 5.0?m multi-wavelength achromatic lens with confocal surface focusing.A design method of a wide-spectrum achromatic lens is proposed.According to the phase response of the sub-wavelength structure to the electromagnetic wave and the P-B phase,the random searching algorithm is used to optimize the structural parameters,and a wide-spectrum achromatic lens with a certain achromatic capability in the 3-5?m band is realized.