Research On Wide-angle Super-resolution Fourier Transform Planar Device

In recent years,the rapid development of the Internet of Things,Big data and Artificial Intelligence and other fields has put forward higher requirements for information storage technology.While traditional information storage methods have short life,high energy consumption and slow access speed,Fourier transform holographic storage has the advantages of long life,low energy consumption,fast access speed and high density.Fourier transform device is the key components of Fourier transform holographic storage systems,and has some widespread applications in spatial filtering,optical computing,photonic chip and other fields.The focal spot of Fourier transform device used for holographic storage is limited by diffraction,so it is difficult to meet the needs of higher-density holographic storage.In order to solve the problem that the focal spot of Fourier transform device is difficult to break through the diffraction limit problem,a kind of design method of super-resolution Fourier transform device based on angular spectral propagation theory and marine predator optimization algorithm is applied here,and uses the sub-wavelength geometric phase metaatom to modulate the optical field,realizes a wide-angle super-resolution Fourier transform device.The main work of this thesis is as follows:(1)This thesis analyzes the research status of Fourier transform devices,and draws the problem that the focal spots of the existing Fourier transform devices cannot break through the diffraction limit,and the research content of this paper is proposed for this problem.(2)The Fourier transform properties of the lens and the Abbe sine conditions as an important criterion for Fourier transform devices are introduced.Based on the theory of angular spectrum propagation,the angular spectrum diffraction formula of light field on the propagation surface of Fourier transform device is derived when linear polarized light incident,and the calculation model of the Fourier transform device is established.(3)A wide-angle super-resolution Fourier transform device with aperture was designed using Marine predator optimization algorithm.The device operates at 632.8 nm,with the numerical aperture of 0.25,the radius of 100λ,the focal length of 70λ,and the aperture radius of 18λ.The design results show that:the maximum FWHM of the focal spot is 1.9282λ,which is less than the diffraction limit of 2.0077λ(0.5λ?NA)in the range of 0~°～65~°of the half-field incidence angle,the maximum SLR of the focal spot is 13%.The linear correlation coefficient between the transverse offset of the focal spot and the sinusoidal value of the incidence angle is 0.9999,and the maximum offset is 40.1μm.(4)The geometric phase metaatom unit structure based on amorphous silicon was designed,and the FDTD simulation verification of the wide-angle super-resolution Fourier transform device was completed.Simulation results show that in the range of half-field of view 0~°～50~°,the maximum FWHM of the focal spot is 1.9982λ,which is less than the diffraction limit,the maximum SLR of the focal spot is 14%.The linear correlation coefficient between the transverse offset of focal spot and the sinusoidal value of the incidence angle,and the maximum offset are consistent with the design results.