Effect of Polishing-Induced Subsurface Impurity Defects on Laser Damage Resistance of Fused Silica Optics and Their Removal with HF Acid Etching
| Autor: | Jing Hou, Lei Zhang, Jian Cheng, Hong-xiang Wang, Jing-he Wang |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2017 |
| Předmět: |
absorbing impurity defects
Materials science fused silica Polishing 02 engineering and technology 01 natural sciences lcsh:Technology law.invention 010309 optics Stress (mechanics) lcsh:Chemistry Optics Impurity law 0103 physical sciences General Materials Science Irradiation Absorption (electromagnetic radiation) Instrumentation ultra-precision polishing lcsh:QH301-705.5 Fluid Flow and Transfer Processes business.industry lcsh:T Process Chemistry and Technology subsurface damage General Engineering 021001 nanoscience & nanotechnology Laser lcsh:QC1-999 Computer Science Applications laser damage resistance HF acid etching Compressive strength lcsh:Biology (General) lcsh:QD1-999 lcsh:TA1-2040 Melting point 0210 nano-technology business lcsh:Engineering (General). Civil engineering (General) lcsh:Physics |
| Zdroj: | Applied Sciences, Vol 7, Iss 8, p 838 (2017) Applied Sciences; Volume 7; Issue 8; Pages: 838 |
| ISSN: | 2076-3417 |
| Popis: | Laser-induced damage on fused silica optics remains a major issue that limits the promotion of energy output of large laser systems. Subsurface impurity defects inevitably introduced in the practical polishing process incur strong thermal absorption for incident lasers, seriously lowering the laser-induced damage threshold (LIDT). Here, we simulate the temperature and thermal stress distributions involved in the laser irradiation process to investigate the effect of impurity defects on laser damage resistance. Then, HF-based etchants (HF:NH4F) are applied to remove the subsurface impurity defects and the surface quality, impurity contents and laser damage resistance of etched silica surfaces are tested. The results indicate that the presence of impurity defects could induce a dramatic rise of local temperature and thermal stress. The maximum temperature and stress can reach up to 7073 K and 8739 MPa, respectively, far higher than the melting point and compressive strength of fused silica, resulting in serious laser damage. The effect of impurity defects on laser damage resistance is dependent on the species, size and spatial location of the defects, and CeO2 defects play a dominant role in lowering the LIDT, followed by Fe and Al defects. CeO2 defects with radius of 0.3 μm, which reside 0.15 μm beneath the surface, are the most dangerous defects for incurring laser damage. By HF acid etching, the negative effect of impurity defects on laser damage resistance could be effectively mitigated. It is validated that with HF acid etching, the number of dangerous CeO2 defects is decreased by more than half, and the LIDT could be improved to 27.1 J/cm2. |
| Databáze: | OpenAIRE |
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