| Metasurface,a kind of well-designed artificial two-dimensional(2D)material,is composed of subwavelength unit structures.It can arbitrarily manipulate the amplitude,phase,and polarization of electromagnetic waves by adjusting the material,shape,size,and arrangement of the unit structure of the metasurface to achieve unusual electromagnetic characteristics.By using the unique properties of metasurface and regulating the variable electric and magnetic responses,it can arbitrarily transform the wavefront and realize various functions devices in terms of applications.In addition,compared with traditional optical components,metasurface has the characteristics such as thinner,more compact,and more flexible in regulation of electromagnetic waves,which can be used to integrate multiple functions in a single device to form a multifunctional meta-device.In recent years,a series of novel functional devices have been realized by utilizing the properties of metasurface that can flexibly regulate electromagnetic wavefront,such as nano-printing,hologram,vortex beam generation,nonlinear optics,optical quantum communication,optical information encryption.However,three-dimensional(3D)vertically stacked multilayer metasurface confronts some challenges such as complex fabrication processes and difficult integration due to the limits of technology.In addition,the metasurface has great limitations in the control of multidimensional optical parameters and information storage capacity due to the limitation of space,which has not fully employed its advantages in the application of multifunctional devices.At present,the existing researches on multifunctional surface integrated devices are still focused on expanding the information storage channel,increasing the adjustable optical freedom,increasing the pixel resolution,and enhancing the space utilization rate.This dissertation focuses on the research of single-layer ultra-thin metallic metasurface which aims at the design of multifunctional imaging meta-devices to realize the application of the metasurface in nano-printing,optical information storage,information encryption and so on.The main contents and innovations of this dissertation are summarized as follows:1.Firstly,we introduce the background and significance of the dissertation topics,briefly present the concept and development of metasurface,and summarize the application of metasurface in optical devices.Finally,we synthetically analyze the research status of multifunctional metasurface and its application prospects in various fields.2.The relevant knowledge of electromagnetic simulation is briefly introduced such as the dispersion model of metal materials,electromagnetic calculation method,and simulation software.Then,the process flow of the samples and the related technical methods are introduced in detail.Finally,the process of designing and building of a home-built microscope of the optical imaging system is elaboratively exhibited.3.A monolayer metasurface consisting of silver nanorods with different orientation angle is designed,which can arbitrarily manipulate the reflection at dual-wavelength by rotating the orientation angles of the nanorods.At the long wavelength range(880 nm to 1000 nm),the reflection efficiency is larger than 90%,and for the short wavelength range(605 nm to 625nm),it is over 80%.The simulation and experimental results show that the proposed metasurface with dual-wavelength and high reflection efficiency.In addition,the monolayer metasurface also can be used to realize complementary grayscale imaging with high resolution at 633 nm and 900 nm,which provides some research ideas and technological supports for the following research works.4.Based on the study of the dual-wavelength complementary metasurface,we adjust the size parameters of silver nanorods and introduce the polarization of incident light as a new degree of freedom to design a multifunctional metasurface.Multiple encrypted information is embedded into the designed metasurface,and the recipients can extract the corresponding secret images with the corresponding keys,which is inspired by digital image steganography.The simulation and experimental results demonstrate that the proposed metasurface can hide two optical information in two independent channels under the cloak of a cover image.This work firstly proposes a strategy that combines optical image steganography with grayscale imaging metasurface,which promotes the application in optical information steganography,high-density optical storage,image display,and other related fields.5.A new coding method is proposed to design a multifunctional metasurface by adjusting the amplitude,polarization,and wavelength of the incident light,which can realize a four-channel grayscale imaging to enhances the storage capacity of optical information.The proposed multifunctional metasurface achieves four channels for the first time,which provides a new idea for the ultra-compact display,high-density information storage,optical anticounterfeiting,information encryption,and other fields due to the advantages of small,light,high storage capacity and so on.6.A monolayer metasurface composed of arrays of silver nanorods with different orientation angles is designed,which can directly read the polarization state of the incident light by collecting the reflected grayscale image generated by the metasurface.The proposed metasurface with a broadband wavelength can be used as a broadband polarization detector,which has a wide application prospect in optical measurement devices,especially in miniaturized and integrated measuring devices. |
