Search

In order to improve laser transmission efficiency at 1053 nm and 527 nm, a potassium deuterium phosphate (DKDP) crystal (a key component of high-power laser systems) needs a bi-layer antireflection coating system on its incident surface. UV-curable polysiloxane coatings with a refractive index varying from 1.500 to 1.485 were prepared through the polycondensation of a methacryloxy propyl trimethoxylsilane (MPS) monomer with a controllable degree of hydrolysis. Additionally, the influence rule of the coating structure on the refractive index was intensively studied, and the primary factors that dominate the hydrolysis process were discussed. Further refractive index adjustment was achieved using only a small amount of dopant based on the polysiloxane coating with refractive index of 1.485, allowing for high antireflection of the bi-layer coating system at desired wavelengths to be achieved. In addition, high laser damage resistance and remarkable mechanical properties of the coating were simultaneously realized through the incorporation of a minor quantity of dopants, which benefited from the successful modulation of the intrinsic refractive index of the polysiloxane coating. [ABSTRACT FROM AUTHOR]

The purpose of this study is to analyze the damage of antireflective (AR) coating over potassium dihydrogen phosphate (KDP) crystal subjected to multi-pulse laser irradiation at low flux under vacuum. Fresh silica AR was characterized as a reference; Atomic Force Microscope (AFM), Scanning Electron Microscopy (SEM), profilometer, and Scanning Near-Field Optical Microscope Photo-induced Force Microscope (SNOM-PiFM) were employed to analyze the characteristics of coatings. The experimental results indicated that the damage of AR coating over the KDP crystal was mainly caused by partial exfoliation, which exposed silica particles beneath the surface. It was found that the accumulated tensile stress led to coating damage with the increase of laser pulse. The initial coating damage was observed to extend and interconnect to form large-area exfoliation. Splitting mechanism of SiO–Si TO3 was observed at vibration mode peaks of 1064 cm−1 and 1096 cm−1showing progressing irradiation damage. Based on this study, it would be helpful to suppress the damage probability of AR coating over KDP crystal applied in high-power laser systems. Moreover, the applicability of SNOM-PiFM method to study the Infrared Radiation (IR) spectra of ultra-thin coatings with transparent substrates was proposed. [ABSTRACT FROM AUTHOR]

The fatigue damage behavior of antireflective coating over KDP crystal under vacuum environment was studied with varied UV-laser irradiation, and the dynamic process from initial damage to complete failure of this coating was obtained. Scanning electron microscope (SEM) and slow positron beam (SPB) technique was employed to study the macro- and micro-defects in the process of evolution. The formation of non-bridging oxygen (NBO) and the variation of O/Si ratio along the direction of coating depth were obtained during the damage process based on X-ray photoelectron spectroscopy (XPS). The idea that oxygen with low binding energy absorbs UV light and produces oxygen defects to induce damage was put forward, and the damage mechanism of sol-gel antireflective coating under UV-laser irradiation was given. • The influence factors of fatigue damage over antireflective laser coating on KDP were verified. • The generation of oxygen-related defects was found very fatal for this fatigue damage. • The defect evolution process of fatigue damage was studied by SPB-DBS method. [ABSTRACT FROM AUTHOR]

Mono-layer silica-based antireflective laser coating with modulated structure has been designed and fabricated, in which cross-linking network structure of polysiloxane was prepared as backbone and porous silica spheres (PSSs) were inserted to create interior porosity. Cured polysiloxane provided dense structure that could both prevent the invasion of volatile organic compounds (VOCs) and improve the mechanical property of this coating, while PSSs endowed this coating with proper porosity to adjust its refractive index and relax the high-power laser energy. With certain structure modulation, excellent transmission and laser-damage resistance of this coating at 355 nm (for the application in high-power laser system) and 1064 nm (for the application in laser-guided component) was both achieved. Meanwhile, the hardness of this coating increased significantly compared with that of the conventional porous silica coating. In addition, qualified VOCs endurance of this coating was also proved, which effectively extended the lifetime of such coating. [Display omitted] • Laser coating with novel structure was fabricated to overcome inherent drawbacks of conventional porous laser coating. • High transmission and LIDT, as well as improved hardness and organic-resistance of designed laser coating were achieved. • The designed coating is suitable for more occasions, providing a potential option to replace conventional laser coating. [ABSTRACT FROM AUTHOR]