Design Of Polarization-independent Multifunctional Metasurface

Metasurfaces are two-dimensional planar structures composed of subwavelength artificial atoms that can flexibly manipulate the electromagnetic properties of incident light,and possess powerful capabilities for controlling light fields.Metasurfaces have broad application prospects in the fields of optics and wireless communication,such as polarization conversion,holographic imaging,ultrathin lenses,and beam deflection.Among them,polarization control is a common method that can achieve functions such as beam array layout and depth-of-field extension.However,in the fields of parallel optical manipulation,imaging,and communication,polarization-insensitive metasurface devices are often required,so it is necessary to consider metasurface structures that are insensitive to polarization.This article proposes two novel polarization-insensitive metasurface structures,which are applied to the arrayed beam generator and extended depth-of-focus lens fields,respectively.These structures provide new ideas and methods for solving the problems of polarization sensitivity,difficult adjustment,severe chromatic aberration,limited defocus depth,complex structure,and poor flexibility that currently exist in metasurface devices.The main contents include:1.This article proposes a wavelength multiplexing multi-channel array beam generator based on genetic algorithm and computer-generated holography(CGH).The generator utilizes the wavelength multiplexing property of the metasurface,which enables the reconstruction of different array beams by changing the wavelength of the incident light.Additionally,the metasurface employs a rotationally symmetric cylindrical structure as the basic unit,therefore,exhibits polarization-independent characteristics.Compared to the stitching of multiple metasurfaces,this wavelength multiplexing array can avoid the splitting of incident beams and the chromatic aberration caused by multiple wavelengths in the same field of view,showing great potential for applications.2.In order to break through the limitations of the forward design method,this article adopts a simple cylindrical sub-wavelength structure as the unit structure and combines it with the ultra-oscillation modulation phase method to reverse design a polarization-independent long focal depth metasurface.The optimized metasurface focal depth is increased to 13.07μm(about 22.3λ),and throughout the entire focal depth range,the lateral half-height full-width value is close to the Rayleigh diffraction limit and the focusing efficiency is above 10%.The results of this article provide new insights into the design of extended focal depth metalens and may find applications in imaging,lithography and detection.