Plasma generation and mitigation of sub-surface defects in fused silica optics via advanced plasma treatment
摘要
Nowadays, the finishing of optical components has drawn the attention of many researchers. The recent optics industries need precise surface quality with negligible subsurface defects. Surface characteristics and bulk properties of optics play a significant role in the performance and life of the optical device. Surface finish and surface integrity requirements of optical elements used in navigation-grade inertial sensors such as gyros and accelerometers are extremely demanding. A novel non-contact medium-pressure plasma process is designed and developed to get an ultra-smooth surface with a minimum sub-surface defect for optical components. In the current study, experiments are carried out at RF power of 80, 40, and 20 W for different plasma chamber pressures, i.e., 5, 10, and 20 mbar, with fixed parameters, i.e., 90:10 gas composition and machining time of 45 min. The results reveal the maximum reduced thickness and material removal rate achieved are 6.67 μm and 0.11 mm3/min, respectively. FESEM images reveal that surface cracks, micro holes, grooves, and tearings are reduced after the plasma processing. Surface roughness value after plasma treatment slightly increases from 2.36 to 2.86 µm without any surface contamination at optimal parametric conditions. EDX outcomes show that elements C, O, Ce, and Si appear on fused silica before processing, and Si, F, and O are observed after plasma treatment. The occurrence of F atoms reveals the reactions during plasma processing with the substrate surface. The contact angle measurements show that the measured contact angle decreases after plasma processing. Moreover, the UV–Vis (ultraviolet–visible) is examined before and after plasma polishing.