Photochromic and Photo‐Thermo‐Refractive Glasses

Abstract

Abstract Inorganic glasses are the main transparent material, which people have long used for observation (windows in buildings, windshields in cars, eyeglasses, prisms and lenses in optical instruments), light delivery (light bulbs, projectors, lasers, optical fibers), and fine arts (crockery, bijouterie, jewelry). The ability of glasses to change coloration after exposure to sunshine was well known since the last century. Photochromic glasses that have completely reversible coloration are made of borosilicate glasses doped with microcrystals of copper and silver halides. These glasses are sensitive to near UV radiation. Photosensitivity can be extended to visible and near IR regions by cooperative breeding of color centers. Induced coloration is a wide band that covers the whole visible region. Photocontrolled waveguides can be fabricated in photochromic glasses. These waveguides can serve as attenuators and mode selectors. Photo‐thermorefractive glasses that have irreversible photoinduced refraction are aluminosilicate glasses doped with silver, cerium, and fluorine. These glasses are sensitive to near UV radiation. Their photosensitivity is comparable with the best organic and inorganic materials, it allows wide variations of exposure because of image amplification in the thermal development process, and it has high diffraction efficiency and high transparency from the UV to the IR region.