RESUMEN
In this article, ammonia and methyltriethoxysilane (MTES) were chosen as vapor phase modifiers for the base-catalyzed SiO2 film. The surface of the film became more dense because of the hydroxyl condensation under the catalyst of ammonia, while the introduction of methyl groups by MTES of vapor treatment hindered the condensation to avoid over-change in film thickness. The hydrophobic of film was improved while the surface roughness of the film increased after treatment. The treated double-layer broadband anti-reflection (AR) coating retains high optical properties with the transmittance of 99.61%, 98.85%, and 99.16% at 355 nm, 532 nm, and 1064 nm, respectively. After exposing to the high humidity condition for 30 days, the broadband AR coating after treatment shows good optical durability, and the transmittance at 355 nm only drops by 0.12%. This vapor surface treatment can find potential application in high-power laser systems and solar cells.
RESUMEN
In a large-scale, high-power laser facility, fused silica optics plays an irreplaceable role to transmit extremely intense lasers. However, the surface fractures, such as surface pit, crack, and scratch and laser damage site, of fused silica optics will shorten the lifetime of the optics and thus limit the output performance of the laser facility. In this work, besides experimental study, finite difference time domain (FDTD) simulation is performed to study hydrofluoric acid-based (HF-based) etching effect on the surface fractures. The effect of local surface curvature on etching rate is discussed and an explicit local-curvature-dependent etching model is proposed. Based on this model, the result from FDTD simulation qualitatively agrees very well with that of the experiment. It is demonstrated that the FDTD simulation is efficient to predict the morphological evolution of the surface fractures during etching. In addition, it is found that the surface fractures will be passivated and HF-based etching can greatly suppress the laser-damage growth of laser-induced damage to the surface site of fused silica optics.
RESUMEN
Silica coatings with continuously adjustable refractive indices and wettability properties were prepared through a sol-gel base-catalyzed process. Adjustment of the molar ratio of water (H2O) to tetraethylorthosilicate (TEOS) was utilized to change the hydrolysis degree of the precursors, and hence change the morphology of the silica particles. With the increase in the H2O/TEOS molar ratio, the morphology of the silica particles changed from a linear net-work structure to a bead-like structure and then to a granular particle structure. A particle growth mechanism was proposed and verified by characterization. As the H2O/TEOS molar ratio increased from 0.3 to 21.0, the refractive indices of the silica coatings increased from 1.132 to 1.328. Meanwhile, a varied H2O/TEOS molar ratio also modulated the surface wettability of the silica coatings. The static water angle of the silica coatings decreased from 145° to 6° by increasing the H2O/TEOS molar ratio from 0.3 to 21.0. Different hydrophilic and hydrophobic coatings could be obtained by simply controlling the H2O/TEOS molar ratio. Silica coatings with different refractive indices and hydrophobic (or hydrophilic) properties were obtained at different H2O/TEOS molar ratios.
RESUMEN
A great deal of intensive research has been conducted to obtain high-quality transparent ultralow-refractive-index and ultralow-dielectric-constant thin films for microptics and microelectronics applications. Here, we report a simple procedure to prepare highly porous silica thin films with high optical quality and water resistance through nano-etching of mesoporous silica films followed by fluoroalkylsilane surface modification. The films possess an ultralow refractive index of 1.03 (800 nm) and an ultralow dielectric constant of 1.30 (100 kHz), to our knowledge the lowest values ever reported in thin film materials. The films are superhydrophobic (water contact angle=156 deg), thus exhibit high moisture stability.