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.
Sol-Gel Route to Inorganic Fluoride Nanomaterials with Optical Properties
A sol-gel method, which is the most significant wet process to prepare solids from liquids, can offer interesting and useful routes for synthesizing inorganic metal fluoride and oxyfluoride materials for applications in optics and photonics. Formerly, heavymetal fluoride glasses were intensively studied for potential use in optical fibres. Now the method is extended to prepare a variety of metal fluorides such as alkaline earth and rare-earth fluorides and oxyfluorides in the form of nanoparticles, thin films and nanocomposites. They can be utilized as antireflective coatings, luminescent materials, VUV materials, IR materials, etc. This chapter describes fundamentals and possible applications of optically useful inorganic fluoride nanomaterials through the sol-gel method.
Venus: Evolution of the Upper Atmospheric Clouds
Abstract The large number of UV photographs taken by different observatories throughout the world are grouped for analysis at the IAU Planetary Photograph Center of Meudon Observatory. Three horizontal V, Y, or psi-shaped dark-hued cloud features are usually aligned along the equator and move 110 m s−1 westward in a planetary-wide rotation. The more intense and distinctly V-Shaped features last several weeks. The smaller scale cloud structures usually show significant changes after each successive rotation in 4 days around the planet. The average UV contrast is 32% but can fluctuate from disappearance to 37%. For periods of several years, the polar areas are sometimes covered by a white cloud. According to a set of photographs taken at Pic-du-Midi, this never occurred between 1962 and 1966 but has happened during 25% of the time for at least one pole since 1967, and only when the planet was in a given half of its orbit. These polar clouds are ephemeral and usually last several weeks or months; they evolve...