Research On Wide-angle Reflection Performance Of One-dimensional Photonic Crystals With Low Infrared Emissivity

With the wide application of infrared detectors,infrared stealth technology has become increasingly important in modern warfare.Using the high reflection performance of the forbidden band in the photonic crystal to obtain infrared low emissivity characteristics can achieve the purpose of stealth.However,the incident angle of the light wave directly affects the position and width of high reflection band of photonic crystal.In order to realize high-performance photonic crystal infrared stealth film,it is necessary to recognize the reflection performance of photonic crystal film under different incident angles.To this end,through the discussion of the wide-angle reflection performance of one-dimensional photonic crystals,we optimize and prepare one-dimensional ternary photonic crystal thin films with high infrared reflectivity in the wide-angle range.The main conclusions obtained are summarized as follows:A series of wide-angle one-dimensional binary photonic crystal design models are constructed.The simulation study results of them show that:the refractive index of the dielectric material,the optical thickness of each film layer and the number of structural periods are the main factors affecting their wide-angle reflection performance;for one-dimensional binary photonic crystals with equal optical thickness,a wider wide-angle high reflection band can be obtained by increasing the refractive index ratio of the material,or increasing the refractive index when the ratio is fixed;constructing a heterostructure or a gradient thickness structure can further broaden wide angle high reflection band.A third material layer is inserted into a one-dimensional binary photonic crystal of equal optical thickness.The simulation study results show that:the one-dimensional ternary photonic crystal structure is another more effective design for broadening the wide-angle high-reflection band.For the 3-5μm and 8-14μm atmospheric window bands,the designed one-dimensional ternary photonic crystals have a wide-angle high reflection band width of2.25μm and 6.08μm,respectively;and the reflectance of the two structures in their respective bands is above 90%when the incident angle changes from 0°to 80°.A wide-angle high-reflection Ge/Zn S/Yb F₃ one-dimensional ternary photonic crystal thin film in the 3-5μm band is prepared.SEM/EDS analysis of the sample cross section show that the structure and composition distribution of each layer meet the design requirements.The reflectance of the samples at different incident angles in the 3-5μm band reach 97.93%（0°）,98.18%（30°）,94.93%（60°）and 92.29%（80°）,which are similar to the simulation results;using the integrating spheres,the wide-angle reflectance of the sample in the 3-5μm band is 96.48%,which is in good agreement with the simulation results of average reflectance with angle[0°,90°)and step size of 1°.In this paper,one-dimensional photonic crystal films are studied to obtain broadband wide-angle high-reflection performance,which provides new ideas for the application of photonic crystals in infrared stealth.