16 - CVD in Optical Applications

Abstract

This chapter discusses the chemical vapor deposition (CVD) in optical applications. Optics is rapidly advancing with the development of the laser and optical storage. Evaporation is the original coating process and is low cost and simple to apply. However, evaporative coatings show a pronounced columnar structure, which causes much light scattering, a high wavelength shift with temperature and time, and a high stress. Thus, evaporation is replaced by other thin-film processes, which are primarily standard and ion-beam sputtering. CVD techniques, such as plasma CVD and metallo-organic chemical vapor deposition (MOCVD) are also useful, especially in high-quality applications or where surfaces of three-dimensional objects are to be coated. Some of the optical applications of CVD include antireflection coatings, reflective coatings, heat and light separation coatings, electrically conductive transparent coatings, and architectural-glass coating. The function of an antireflection (AR) coating is to reduce the surface reflection of optical elements and increase the amount of light transmitted. The glare and ghost images from secondary reflections are minimized. The AR coatings are used in numerous applications such as lasers, lenses for cameras and binoculars, instrument panels, microscopes, and telescopes.