Design,Manufacture And Application Of Ultra-broadband Dispersion-controlled Metasurface

Dispersion is one of the properties of optical materials,whose main characteristic is the decomposition of compound light into monochromatic components at different spatial locations.Thanks to the spectral properties of dispersion,it can be applied in the fields of optical communication,hyperspectral imaging and optical communications.On the other hand,the chromatic aberrations caused by dispersion can cause many problems,which are mainly reflected in the imaging of optical lenses.As one of the key components of precision optical systems,lenses have important applications in aerospace,medical devices and consumer electronics,so how to better eliminate chromatic aberration has been one of the hot topics of research.Compared to conventional glued lens sets,metasurface is a multifunctional device designed by subwavelength structure,which is small in size,easy to integrate and can realize multi-parameter control.Therefore,the design and preparation of related metasurface devices can be done according to the dispersion requirements of different devices,so that high quality imaging can also be achieved while meeting the requirements of small size and light weight of the lens for some systems.In fact,to date,no researcher has been able to achieve arbitrary dispersion modulation from visible to near-infrared wavelengths using a single-layer metasurface.In response to the above problems,this article will carry out a series of work related to dispersion modulation based on the relevant principles of metasurfaces.The first part of this paper is to analyze the phase control mechanism of the metasurface light field,studies the phase response of the nanostructured unit and the wavefront phase profile of the metalens The design of an achromatic lens for the visible wavelength band(450-750 nm)is then based on the common linear phase compensation method,which does not fit well with the dispersion relationship of the nanostructured units themselves,so there are large errors in matching the structures and it is difficult to achieve ultra-broadband achromatic.Accordingly,this article proposes a nonlinear dispersive phase compensation approach to design polarizationinsensitive achromatic metalenses from 400 to 1000 nm constructed with single-layer high aspect ratio nanostructures.And this band matches the response spectrum of a typical CMOS sensor for both visible and near-infrared imaging applications without additional lens replacement.The second part of this article investigates how to achieve the fabrication of high aspect ratio structures,introduces the entire conformal filling process and optimizes the relevant process flow.Finally,the preparation of metasurfaces were completed using the equipment available in the laboratory and the prepared samples were characterized by optical microscopy and scanning electron microscopy.In the last part of this work,two sets of optical test platforms were designed and built to test the prepared metasurfaces,and error analysis was carried out based on the test results and the next design optimization directions were proposed.In summary,this paper proposes a design method for nonlinear dispersion modulation,and prepares an ultra-wideband dispersion modulation metasurface through the conformal filling process.Finally,the effectiveness of the scheme is demonstrated by comparing the theoretical design,simulation results and test results.