Capping a glass thin layer on the etched surface via plasma chemical vapor deposition for improving the laser damage performance of fused silica.

Buffered HF-based etching can effectively improve the laser damage resistance of the fused silica, but deep etching would cause the deteriorations in surface roughness and hardness, and decrease the laser-induced damage threshold. Capping a glass thin layer on the etched surface via plasma chemical vapor deposition in one step could overcome those deteriorations. We found that the deposition of the glass thin layer can further reduce the impurity element contamination and the PL intensity while retaining the low subsurface defect density as well as for the deeply etched sample. The surface quality, surface hardness and the laser damage resistance of the fused silica can be significantly improved by the glass thin layer, which reveals the potential application in high power laser facility.

[Spectroscopic Diagnosis of Atmosphere High Frequency Air Plasma Electron Temperature].

Atmosphere high frequency plasma is widely used due to its advantages of free of electrode pollution, high energy density high temperature and controllable redox conditions. As the key parameter in practical use, electron temperature of plasma is commonly diagnosed with atomic emission spectroscopy and calculated with Boltzmann plots. But electron temperatures calculated based on different lines by different researchers are usually not comparable due to transition probability data, application environment, instrumental error and data processing. This paper discussed influences of element and spectral range on calculated electron temperature for the first time in order to obtain reliable electron temperature of atmosphere high frequency air plasma. 7-channel high resolution fiber spectrometer with measurement range of 200~1 077 nm was used to test atomic emission spectroscopy. The experiment indicates that: The R square of fitted slope is 0.95 and standard deviation is the lowest using N Ⅰ lines in 738~940 nm and the calculated electron temperature is the most reliable; electron temperature calculated with Si and O lines are unreliable because they are easily binding to heavy SiO2 particles; reliable electron temperature also cannot be obtained by mixed Ar lines.