Nonlinear Colorful Holographic Metasurface Design Based On Dielectric Materials

Since its discovery,nonlinear optics has attracted the attention of researchers and has been widely used in laser modulation,photoelectric switching,frequency conversion,optical parametric oscillators,and optical information encryption,etc.The metasurface is composed of sub-wavelength micro-nano structures,which can manipulate the amplitude and phase of light.Nonlinear optical metasurface is a collective term for a class of metasurface devices.Due to their high nonlinear conversion efficiency,simple to be prepared and compact structure,it has occupied a pivotal position in the optical area.This paper studies the application of metasurfaces in holographic display and nonlinear conversion,and combines nonlinear optics and holographic imaging to design and verify the nonlinear holographic metasurface.This method can be used for information encryption and low-noise holographic imaging.The main content includes the following aspects1)In this paper,by choosing the ultra-low absorption silicon,the conversion efficiency,electric field distribution and phase of nanostructures are simulated.Filter out the most suitable cell size for different wavebands.The pure phase hologram is calculated by the Gerchberg-Saxton(GS)algorithm and encode to metasurface.The accuracy of holograms and the feasibility of metasurfaces as hologram coding materials are verified by simulation software.Proposed and verified a method of achromatic processing on the holographic metasurface performance parameters are studied.2)Due to the problem of low conversion efficiency of pure metal or pure medium nonlinear metamaterials,the metamaterials mixed metamaterials were proposed.By adjusting the structure of the unit,a multi-band resonant metal structure is designed.By means of the coordination of multi-band resonance,isoplasmon resonance is formed in both fundamental wave band and harmonic wave band to form pattern matching.The dark state at the fundamental frequency can use energy to gather,while the bright state at the double frequency is more conducive to radiate the second harmonic signal.The nonlinear medium material is used as a "converter" to form an efficient nonlinear conversion.3)Through the design of Ga As cell structure,the metasurface can produce resonance enhancement at both 1200 nm and 840 nm.The resulting strong electric field enhancement enables the structure to facilitate the nonlinear conversion,generating frequency doubling light and frequency summing light.Based on the verified holograms,the nonlinear PB phase coded holograms are applied to the nonlinear metasurface.Simulation software is used to verify the feasibility of holographic imaging of nonlinear metasurface in the second order nonlinear optical band.The design idea of this thesis will provide valuable reference and guidance for nonlinear color holographic metasurface.The research results provide more ideas for the application of optical metasurfaces in frequency conversion and holographic imaging.