## 1 Introduction  
Fused silica is widely used in the field of high-energy laser systems due to its excellent physical and optical properties [1, 2]. And laser damage resistance performance has become the primary goal due to the damage and failure of optical components caused by high-flux laser irradiation. In order to improve the laser-induced damage threshold (LIDT) of fused silica, many scholars internationally are committed to researching the processing methods for obtaining the intrinsic surface of high-power optics [3, 4, 5, 6, 7]. With the deepening of research, researchers have gradually realized that chemical structure defects generated by pre-processing are one of the main damage precursors under higher flux (12-16 J/cm\({}^{2}\)) laser irradiation. However, relevant research is not sufficient, the generation rules are not clear, and there is also a lack of effective suppression methods. How to further improve the laser damage resistance performance of fused silica has become a hot and major scientific problem, and manufacturing research for higher flux laser irradiation is imminent. Current research has shown that it is difficult to achieve comprehensive and effective suppression of damage precursors by a single post-treatment process [4, 5, 6, 7, 8]. Therefore,exploring the theories and methods of combining multiple post-treatment processes to suppress defects has become an inevitable choice to realize the low-defect surface manufacturing of high-energy optics. Based on the high removal efficiency of HF acid etching and the low damage characteristics of IBS, our research team has explored this combined process. When IBS is used to remove a certain depth (<1000 nm) of HF acid-etched surface, it can reduce the concentration of oxygen deficiency center (ODC), non-bridging oxygen hole center (NBOHC), and OH- groups on the surface, weaken the photothermal absorption intensity, and increase the LIDT of fused silica components by 30% compared with that of the single HF acid etching method. This preliminary verification verifies the good effect of IBS in suppressing chemical structure defects [9; 10; 11; 12]. The IBS processing technique has the advantage of modifying the surface and physical properties of many optical films [13; 14; 15]. Irradiation through ionizing radiation has been developed to bring about changes in the form of thermal absorption or oxidation in the oxide thin film's structure and physical properties. IBS has also become one of the most promising new processing methods for suppressing chemical structural defects. However, with the emergence of new phenomena and the deepening of research, it has been gradually realized that IBS has two sides in the regulation of chemical structure defects, which can not only remove chemical structure defects generated by pre-processing but also produce sputtering damage on its intrinsic surface, but the process conditions and generation mechanism of the two-sided effect are still unclear. The regulation law of IBS on chemical structure defects is not well understood, and the research on the combination sequence and process interface conditions of the combined process is not fully studied, which cannot provide technical guidance for effectively suppressing surface chemical structure defects. The OH- groups in fused silica are both impurity defects and chemical structure defects. They break the Si-O bonds in the silica network, reduce the chemical stability of the substrate surface, and also affect the existence of other types of structure defects, seriously reducing its laser damage resistance performance [16]. Our team has studied the evolution law of chemical structure defects on fused silica surfaces during the combined process of HF acid etching and IBS [4; 8; 9; 10; 11]. It was found that the hydroxyl content on the sputtering surface increased after being cleaned with deionized water, and the photothermal weak absorption intensity also increased while the LIDT decreased significantly.