Research On Key Technology For Laser Damage Testing Of Optoelectronic Materials

With the development of high-power and high-energy laser technology and its application,the problem of laser damage on the surface of photoelectric materials becomes more and more prominent.To master the damage process and damage characteristics of photoelectric materials has become a hot spot of laser technology development in recent years.Aiming at the problem of high-energy laser damage to optoelectronic materials,this paper has carried out research on some key technologies in a high-power laser damage testing system with optoelectronic protective materials being the research object,and conducted simulation and experimental analysis.The research results will provide scientific basis for developing photoelectric materials with high laser damage resistance and promote the development of preparation technology of photoelectric materials with high damage threshold.First of all,through studying and analyzing the current research situation at home and abroad,this paper introduces the laser damage mechanism of photoelectric materials and the laser damage testing principle.On this basis,a strong laser damage testing system is designed,and the implementation schemes of the power density calibration unit and synchronous imaging technology are deeply discussed.According to Hough circle transform method,the effective area of laser spot is calculated,and the proportional relationship between the laser power of the tested optical path and the calibrated optical path is obtained by calibrating the spectral ratio,so that the accurate calibration of laser power density is realized,and the uncertainty of power density is calculated,which provides a basis for the accuracy of measurement results.The optical fiber spectrometer is used to test the plasma spectrum generated in the process of laser damage.According to the plasma spectrum curve,the filter and illumination source in the high-speed camera unit are selected,and then the dichroic mirror is selected.The synchronous imaging analysis software for laser damage testing is optimized to achieve online monitoring of the laser damage process of photoelectric materials.Then,the interaction process between high power continuous laser and material is simulated by using the finite element method through COSMOL Multiphysics software.Based on the heat conduction equation in cylindrical coordinate system,the finite element theoretical equation of material temperature field is constructed through finite element discretization,unitization and overall analysis.Based on the theory of interface heat transfer,a one-dimensional finite element equation of heat transfer between coating material and substrate material is derived.Taking the existing photoelectric protection materials in our laboratory as test samples,the laser damage test experiment is carried out,and the damage process is photographed by high-speed camera.Combined with the simulation results of temperature field,the damage process is dynamically analyzed,and the morphological evolution law of the samples under intense laser irradiation is obtained.Finally,aiming at the problems of high noise and low contrast in damage images obtained by high-speed cameras,a damage area calculation method based on depth learning method is proposed.The basic steps of using U-Net network models to segment damage areas are introduced,including the selection of network models,production of data sets,algorithm evaluation indicators during training,loss functions,and selection of optimizers.Good damage area segmentation results are obtained.According to the calibration results of a single pixel size of the high-speed camera,the actual damage area is obtained by traversing the number of pixel points in the damage area,which proves the feasibility of this method.The difficulty of accurately measuring the damage area in low contrast damage images has been overcome.