Silicon-based Metasurface For Structural Color Display And Dynamic Holographic Switching

To satisfy human visual experience,and transmit and reproduce true color information,the pursuit of high performance and multi-function color display has become one of the goals of the display field.Inspired by the bright colors of the micronano structures on the surface of some plants and animals that interact with light in nature,scientists have started the study of micro-nano based structural color devices.In recent years,due to the rapid development of micro-nano processing technology,structural color and holographic display devices have become an important research field of nanophotonics by using two-dimensional metasurface composed of micronano structure to tailor the amplitude and phase of light.With the advantages of silicon,titanium dioxide and other dielectric materials,such as low cost,high refractive index and compatibility with existing CMOS technology,the display devices of metasurface have made rapid development.However,the performance can not meet the requirements of the new generation of display technology for wide color gamut,high brightness and resolution,and multi-functional regulation,and the performance and application potential of micro-nano structure have not been fully exploited.Among them,the multi-parameter structural color design,highperformance structural color display technology and dynamic holographic display technology using structural color expansion have not been breakthrough.In response to the challenges faced by the above-mentioned metasurface structural color,this paper combines the urgent needs of high-performance and multifunctional structural color in the information field to conduct research and application of monocrystalline silicon-based metasurface from three aspects: First,nanoring and C-shaped nanoring structure which can be optimized by multiple parameters are designed to realize the application of full color display with wide color gamut and anomalous refraction.Second,the design of refractive index matching layer makes the structural color achieve the breakthrough of five key performance parameters at the same time and improve the application value of structural color.The third is to use the design of bifunctional metasurface,which integrates color and dynamic holographic display functions and expands and enriches the application functions of structure color.The specific research content is as follows:The nanoring structure with inner holes is prepared,and the amplitude of incident light in visible light can be controlled in a wide range by multi-parameter regulation of outer radius and inner radius.After optimization design,150% of the s RGB is realized,and the fabrication process of HSQ negative photoresist is developed and optimized.The high-quality ring structure is prepared,and the high brightness color display covering the visible light is realized,and the reflection in the blue region realizes 70%.Further by designing the C-shaped nanoring structure with open angle,four dimensions of the outside radius,inside radius,period and opening angle can be optimized to obtain 8 types of cell structures covering 0-2? phase.The anomalous refraction application was realized.By adding refractive index matching on the monocrystalline silicon metasurface,the reflection of the substrate and wide resonance peaks are suppressed significantly,and the color gamut of the display is greatly improved.It is the first time to experimentally demonstrate an all-in-one solution(i.e.,gamut,brightness,FWHM,resolution,manufacturability)for structural color.The highest recorded value of gamut is achieved,around 97.2% of Rec.2020.The highest display brightness reaches76%.The FWHM of the reflection peak can reach 34 nm,and the highest resolution exceeds 100000 dpi.This progress routes a key step towards the commercial application of structural colors in the fields of wide-color gamut and high-resolution displays,color nano-printing,and biomolecular detection and sensing.To expand the functional application of structural colors,a dynamic bifunctional metasurface is realized by integrating holographic display into the design of structural colors.The design of monocrystalline silicon nano-elliptical pillars is used to control the amplitude of the circular polarization and the Pancharatnam-Berry phase at the same time.The gamut of structural colors can cover 121% of s RGB in white light mode and display the colorful cartoon pattern.The projection of far-field holographic images can be realized in the laser irradiation mode.Besides,the design of the holographic display integrates the dynamic control function by using the external refractive index of the environment to control the amplitude.After adding solution,the holographic image at particular wavelengths can be switched between "on" and "off",or "unchange" states.The switching time of the holographic image can reach16 ms or less.This research expands the dynamic functional application based on the metasurface structural color and further enhances the application value of the metasurface structure color in the fields of microfluidic dynamic display,optical security and information storage,and functional dynamic color control.