| A study was conducted to understand the effects of etch time on the damage threshold of fused silica substrates. The study used a 355nm,10ns,3Hz Nd:YAG laser to damage test .Laser surface damage threshold of fused silica after hydrogen fluoride etching are increased by 53.1%. The strengthening mechanism is analyzed. We have measured the growth of laser-induced damage in the air. The result shows exponential growth in the lateral size of the damage site with shot number. A different investigation of testing data also have a important role on laser damage threshold , another damage threshold was obtained by eliminating the bizarre data used Nomarski microscope. Comparison between these two values and contrasting them with the experiment results, and made it more close to the "real"damage threshold. Study in detail the technical plan of laser conditioning device(Nd:YAG laser with wavelength 1064nm) and the laser conditioning process, experiment demonstrate that the laser conditioning can improve the HfO2/SiO2 coatings damage threshold up to 3 times.The micro-structure and laser damage threshold of nano-ZrO2 thin films were investigated. The experimental results showed that the crystallitic size and different micro-structure influence the laser damage threshold. The obtained results showed that laser damage threshold of polycrystalline structure is obviously higher than that of amorphous structure. Automated testing using He-Ne scattering light device was set up. HfO2/SiO2 coatings were tested, and compared with plasma spark method and phase contrast microscope method. The results show He-Ne scattering technique is a effective, reliable technique. Plasma spark method is based on laser induced damage theory, but plasma spark intensity varies with different film material and plate fashion, and it is difficult to detect on line. Phase contrast microscope observation method is the international standard detection method, but it can't detect some damages and is difficult to detect on line.
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