Simulation And Reconstruction Of 3D Microscopic Morphology Of Damaged Surface

In the application field of high-energy laser,Laser-Induced Damage Threshold and damage identification of optical elements have already caused high attention.Researchers are devoted to the analysis and research of the damage process caused by the laser film element,as well as the damage characteristics of images with the help of the reconstruction of the three-dimensional micro-morphology of the optical thin film damage surface.They hope to reveal the damage mechanism and provide technical support for thin film preparation and damage identification.In this paper,based on the principle of white-light interference microscopy,the interference microscopic 3D point cloud data of the damaged surface was sampled.And then,the characteristics of actual damage morphology of thin film elements induced by laser were combined,and with the Delaunay triangulation method,the damage on the surface of the triangular mesh model was constructed.Through visual simulation,the reconstruction and reproduction of the damaged surface were realized.Moreover,the cause and mechanism of film damage were explored.The main research work is as follows:For the accuracy of the digital three-dimensional topography information of the damaged surface accurately,combined with the randomness of laser damage of optical thin films and based on comparing and analyzing the principles,merits and demerits of various micro-surface 3D topography point cloud data acquisition methods,the white light interference microscopy technology is selected to gain the point cloud data of the damaged surface.Monolayer optical films of hafnium dioxide(HfO2),silicon dioxide(SiO2)and titanium dioxide(TiO2)under the action of pulsed laser are taken as the object of study.Electron beam evaporation method is used to complete the preparation of all thin films,which is done on K9 glass substrate.Besides,the change of substrate shape before and after coating,and the density of film formation were tested.The test results show that the prepared HfO2 and TiO2 thin films show tensile stress.On the contrary,SiO2 thin films show compressive stress.In addition,the density of SiO2 films formation is the highest,followed by HfO2,and that of TiO2 films formation is relatively loose.Based on the Delaunay triangulation algorithm,the triangular mesh model of the damaged surface is established by inserting mesh point by point.The damage surface is reconstructed and reproduced by writing C++program code.The whole process is completed under the development environment of Visual Studio 2010 software,which is configured the Visualization Toolkit.Before modeling,it is necessary to preprocess the acquired original point cloud data,select the effective data and eliminate the invalid data,which can not only reduce the amount of point cloud data,but also eliminate the influence of noise on the calculation program and model quality.The reconstruction results show that the damage morphology of the reconstructed monolayer HfO2,SiO2 and TiO2 thin films is pit-shaped,which is generally characterized by thermal damage and heat-induced stress damage.Furthermore,the complexity of damage morphology is diverse.And the edge steepness of the damage area varies greatly,where exist many bulges,cracks and deep pits.To better explore the film damage morphological characteristics and dynamic damage process,after analyzing the damage morphology of different thin films,it is found that the damage area of HfO2 and TiO2 films is single damage spots,while that of SiO2 films shows multiple damage spots.Under the same cumulative effect of pulsed laser,the longitudinal height of the damage area of HfO2 films is the largest,and the damage morphology is the most complex and changeable;The SiO2 film is following on,and its damage morphology is relatively gentle;In addition,the peak and valley values of TiO2 films are the smallest.Finally,the reconstruction effect is compared with the measurement results of the non-contact profiler with the measurement accuracy of 0.1nmto verify the accuracy of the reconstruction,and the results indicate that the accuracy of the two is "equivalent".In this paper,the three-dimensional microscopic damage morphology of optical thin film elements under the action of laser was modeled,simulated and reconstructed.And then,the dynamic damage process and mechanism of optical thin film components are explored and studied.The results provide technical support for analyzing the morphology of damaged surface and regulating the preparation process of optical thin films with high LIDT.