1. Lenses and optics

Glass is a homogeneous, isotropic material with intrinsic properties that are unique in the field of optics. Glass is homogeneous at length scales well below those of visible wavelengths. If properly prepared, it contains no imperfections that could cause refraction or internal reflection of incident light.

Oxide glasses and a few fluoride glasses are chosen for most optical applications in the visible range. Their transparency is not their only advantage. Mineral oxide glasses are harder than conventional steels. Above all, they are easy to shape by molding, pressing or drawing. High-precision pressing now achieves dimensional accuracy better than a hundredth of a millimetre, with roughness below 10 nm. Some aspherical lenses are made by pressing. Optical fibers for telecommunications are manufactured by drawing.

At room temperature or...