Investigation of MgF2 optical thin films with ultralow refractive indices prepared from autoclaved sols.
We have successfully developed a process to form high quality MgF(2) thin films with ultralow refractive indices from autoclaved sols prepared from magnesium acetate and hydrofluoric acid. And we have confirmed that our porous MgF(2) coatings have not only high transmittance in the UV region but also high uniformity of film thickness. They can be uniformly formed on phiv 300 mm substrates as a single coating and as a hybrid coating with sublayers formed by physical vapor deposition. They are expected to be applied to various optics that need high transmittance in the UV region.
High-performance antireflective coatings with a porous nanoparticle layer for visible wavelengths.
Ghosts and flares are well-known problems that are caused by reflections from lens surfaces when we take photographs. It is more difficult to prevent such stray light in a digital camera than in a film camera because of high reflectance from the low-pass filter and diffraction from the image sensor. To prevent such stray light, we introduce an ultralow refractive index layer into the antireflective (AR) coatings. We used the solgel method to form porous fluoride layers with ultralow refractive indices, and we succeeded in developing a unique process to form AR coatings with superior performance.
Interference coating by hydrophobic aerogel-like SiO2 thin films
Abstract The present paper presents a novel method of preparation of hydrophobic aerogel-like SiO2 thin films by means of a two-step acid/base derived silica sol at an ambient pressure without any supercritical drying. Crack free aerogel-like SiO2 thin films having thickness of 100–400 nm, and refractive indices of 1.13–1.25 have been obtained upon heating at different temperatures. By using the silica aerogel-like thin films as low-refractive index component and sol–gel derived TiO2 as high-refractive index component, a two-layer refractive index gradient SiO2 hydrophobic anti-reflective (AR) coating and a 12-layer SiO2–TiO2 near infrared reflective (NIR) coatings have been successfully deposited on glass substrates. The obtained AR coatings have shown average reflectance of ≤2% in the wavelength range 1000–2000 nm. A minimum transmittance of ≤2% in the wavelength range between 995 and 1085 nm, and the maximum transmittance of ≥80% in the visible range has been obtained from the deposited 12-layer SiO2–TiO2 NIR multilayer reflective coatings.