| Optical components of high power laser systems have no same laser-induced damage threshold (LIDT), and usually the function of the laser system is limited by some or other component. It is showed by the results of the experiments that a particularly weak point is the components with optical coatings, which have become a key problem hampering the further increase in the output of laser equipment. The important factors which have influence on the laser-induced damage threshold of thin films are (1) the substrate, the coating materials, and the coating design; (2) the deposition technology of the coatings, the substrate treatment before deposition, and laser pre-conditioning; (3) laser parameters. The magnitude of the damage threshold is the most direct and comprehensive reflection on these factors, though the three factors have a complex interaction among them,.In the paper , the mixed HfO2+Al2O3 coatings are, firstly, successfully manufactured after a new electron-beam evaporation installation is fixed and regulated, some research work, concerning the choice of coating materials, the cleaning technique of K9 glass substrates, the thin film deposition, the properties of thin films, and the LIDT, has been finished. The theories of the laser irradiation damage, concerning avalanche ionization, multi-photon absorption, and impurity-initiated laser-induced damage, are treated and compared among their characteristics, while the selective rule of the coating materials with the high damage threshold is obtained, i.e. the dielectric materials with the larger band-gap energy are selected. The primary criterions of the laser irradiation damage, concerning the transmission and reflection light method, the scattered light detection method, and plasma spark method, are studied in our experiments. The following new results are obtained.1. The new electron-beam evaporation installation is fixed and regulated.2. The mixed coating materials are selected to improve the damage threshold of the thin films, and the cause for the HfO2+Al2O3 coating materials is analyzed. The analytical result has not been reported.3. The HfO2+Al2O3, ZrO2+Y2O3, HfD2, and A12O3 coatings are successfully manufactured. The mixed HfO2+Al2O3 coatings are, for the first time, manufactured at home, and the optimized depositing technology refers to the following deposition condition, i.e. ratio of the HfO2 (90 wt% ) to the Al2O3 (10 wt%), original vacuum 2 X 10-3Pa, working vacuum 6 X 10"3Pa, electron-gun power 0.98-1.05kW, substrate temperature 250癈. The results of the X-ray Photoelectron Spectroscopy (XPS) illustrate that the ingredient of the mixed HfO2+Al2O3(90:10wt%) films is well-proportioned, and the thresholds of this films are higher in comparison with that of the thin films offered by other manufacturers using the e-beam deposition technique. The research contents and results have not been reported.4. The preparation of the ZrO2+Y2O3 filmsThe thresholds of ZrO2+Y2O3 (80:20wt%)films with the different thickness have no relation to the film thickness. The surface roughness decreases rapidly with the increase in the thickness in the range of 200nm, and then decreases gradually with the increase in the thickness beyond the range of 200nm, and finally is close to the surface roughness of K9 glass substrates.5. The results of the X-ray Diffraction (XRD) illustrate that the construction of the various films manufactured is at all amorphous. The results of the XPS illustrate that there is carbon and moisture on the surface of the films, but no metallic impurity contamination. The films have a steady refractive index obtained by the elliptical polarimetry.6. The laser damage morphology of thin films is observed and analyzed by means of the phase contrast microscope, the scanning electron microscope, the atomic force microscope, and the method of moisture, and divided into six sorts. The method of the damage observation with the scanning electron microscope has not been reported at home.7. The LIDTs of the films is studied, and t...
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