Research Of Controlling Visible-Infrared Spectrum Characteristics Based On Micro-Nano Multi-Layer Structure

In recent years,with the rapid expansion and integration of visible-light identification and infrared opto-thermal detection,the conventional target object with the single-purpose and single-waveband camouflage has been directly exposed;as a result,the probability of detection is significantly increasing.Therefore,as an effective approach of controlling spectrum characteristics,visible-infrared compatible camouflage materials or structures for applying to the target surface have become a research hotspot in the current and future military anti-reconnaissance field.However,the available compatible camouflage methods now still exist the following two deficiencies:poor camouflage color attributes or high infrared emissivity.For this purpose,based on the micro-nano multi-layer structure model,we have systematically proposed two types of new structural systems for visible-infrared compatible camouflage;then from the standpoint of electromagnetic transmission characteristics and physicochemical properties of materials,we have lucubrated the objective laws of various related performance parameters and internal function mechanism of them for compatible camouflage applications.The main contents are as follows:Firstly,we have investigated the mechanisms of photonic bandgap?PBG?at infrared atmospheric window and the color-forming from equal inclination interference.Based on them,we have proposed the series-design principle for compatible camouflage of micro-nano multi-layer structure and successfully prepared?monochrome camouflage?-?low infrared emissivity?compatible camouflage structure H_s/Ge?ZnS/Ge?³?H_s is the thickness of interference layer ZnS?.Moreover,we have further analysed the glossiness-weakened ability of sub-micron polytetrafluoroethylene?PTFE?from micro-morphology,electromagnetic response and color attributes.We have eventually designed and prepared?monochrome camouflage?-?low glossiness?-?low infrared emissivity?triple series-wound compatible camouflage structure PTFE/H_s?Ge/ZnS?³.Secondly,we have investigated the polarized-separated color quantization mechanism of oblique incidence CIE?Commission Internationale de L'Eclairage?in detail,and have systematically deduced and proposed four kinds of polarized-separated?s polarization and p polarization?characteristics of main color parameters?tristimulus values T_v,luminance factors Y%and chromaticity coordinates CCs?at obliquely incident angles?45^°,60^°and 75^°?:arithmetical averaging characteristic of T_v or Y%,collinear characteristic of CCs,constant mathematic relation of T_v?s?>T_v?p?or Y_s%>Y_p%,synthetic CCs partial to s-polarized CCs.Then relying on the coupling mechanism between electromagnetic reflection response R???and color attributes,we have designed a bran-new characterization method“Two-step Method”for polarized-separated color parameters of oblique incidence,which has verified the aforementioned deductions.Thirdly,we have investigated the mechanism of multi-PBGs splicing and digital camouflage constraints in depth.After partitioning and calculation for complex interface structure with finite element method?FEM?,we have proposed the design principle for digital camouflage of dielectric film and prepared surface graphical photonic crystal?SGPC?for?visible digital camouflage?-?low infrared emissivity?compatible camouflage.Then we have quantificationally analyzed the advantages of thickness-progressive quasi-periodic structure on effectively broadening PBG and thinning physical thickness d.Based on reflection response,color attributes and 3D electric field distribution,we have also systematically investigated the spatial coupling performance of digital camouflage,which combines 7digital camouflage textures?x-y plane?and 3 interference colors?z direction?.Furthermore,proceeding from the change law of three color parameters and buffering effect of multi-PBGs,we have revealed the applicability of digital camouflage for oblique incidence and angular insensitivity of infrared transmission.Finally,in order to significantly improve color attributes of metal-based micro-nano multi-layer structure,we have further investigated the mechanism of enhanced Bragg reflection for the interface of metal?M?-dielectric?D?and the skin effect for high-frequency.Based on the designed sandwich structure M-D-M,we have systematacially proposed the design principle of matching equal inclination interference effect from the upper interface M-D with enhanced reflected intensity,then prepared the Ag-based interference-enhancing surface graphical structure SiO₂/Ag/ZnS/Ag for visible-infrared compatible camouflage.We have also investigated the angular insensitivity of main camouflage parameters.Based on the switching mechanism between metallic?high infrared reflection?and nonmetallic?visible-light translucency?effect,we have eventually obtained high-performance Ag-based tri-color camouflage?yellow,blue and cyan?and low infrared emissivity compatible camouflage structure.