Research On Infrared And Laser Compatible Stealth Materials Based On One-Dimensional Photonic Crystals

With the rapid development of all kinds of detection technology,the survival of weapons and equipment has been greatly challenged.Improving the full-band camouflage stealth capability of weapons and equipment is an effective means to protect military facilities and reduce the probability of personnel damage.Among them,there are substantial problems in the mechanism of infrared and laser compatible stealth.Infrared stealth requires higher reflectivity of the target surface,while laser stealth requires low reflectivity.It is difficult to achieve a better compatible stealth effect relying on traditional materials.Therefore,to enhance the infrared and laser compatible stealth ability of weapons and equipment is still a challenge in the field of camouflage stealth.In this paper,one-dimensional photonic crystal thin film materials with infrared and laser compatible stealth properties are designed and prepared to achieve infrared and laser compatible stealth effect.According to the characteristic matrix theory of optical thin films,one-dimensional photonic crystal structure with alternating stack of periodic units of high refractive index germanium and low refractive index materials magnesium fluoride,zinc sulfide,zinc selenide and silicon is simulated by TFCalc software.The effects of refractive index difference,period number,defect layer and insertion form of defect layer on the spectral reflection curve of one-dimensional photonic crystal were investigated.The composition materials and film stacking structure of one-dimensional photonic crystals were determined.According to the requirements of infrared and laser compatible stealth,the structure of one-dimensional photonic crystal thin films with high reflection region in 3 ～ 5 μm and 8 ～ 14 μm and low reflection region in 5 ～ 8 μm and 10.6 μm is designed and optimized.This is used as a theoretical basis to guide the preparation of follow-up thin films.One-dimensional photonic crystal thin films were prepared with germanium and zinc sulfide on glass substrate and flexible Polyethylene Terephthalate(PET)substrate using magnetron sputtering.The effects of different sputtering power on the growth rate,film quality and refractive index of germanium and zinc sulfide thin films were analyzed and characterized by Scanning Electron Microscope(SEM),Atomic Force Microscope(AFM)and Ellipsometer.It is shown that in a certain range,the growth rate of germanium thin films increases with the increase of sputtering power,in which the mean square roughness of germanium thin films decreases from 14.7 nm to 6.93 nm and then increases to 14.5 nm,and the mean square roughness of zinc sulfide films decreases from 6.31 nm to 3.96 nm.In the preparation of one-dimensional photonic crystals,the sputtering power parameters with faster film growth rate and less roughness should be selected to ensure that the growth thickness of the film can be accurately controlled and higher film quality can be obtained.After the sputtering power of germanium film and zinc sulfide film is determined,one-dimensional photonic crystals are prepared according to the calculated arrangement and stacking method.The cross-sectional morphology of the samples is characterized by SEM,the multi-layer structure of photonic crystals can be obviously observed,and the infrared reflectivity curve is characterized by Fourier Transform Infrared(FTIR).The average reflectivity is 86.9% in the range of 8 ～ 14 μm,and the transmittance is 70.4% at 10.6 μm.It can basically meet the requirements of infrared and laser compatible stealth,and the infrared stealth is further verified by infrared thermal imager.It is found that the prepared sample has good infrared stealth performance.In order to broaden the practical application range of the prepared material system,one-dimensional photonic crystal thin films were prepared using flexible material PET as substrate.Cyclic bending experiments and maximum bending experiments were carried out to test the bending resistance of flexible one-dimensional photonic crystal thin films.The results show that the one-dimensional photonic crystal thin films can still maintain the intact structure after 1000 cycles.When the bending Angle reaches 150°,the film layer fell off,indicating that its structure was damaged.