Abstract
This chapter summarizes silica optics that is preferred for many optical systems. Silica Optics have some important features:(1) excellent optical transmission from the ultraviolet (170 nm) to near infrared wavelengths (3400 nm), (2) excellent refractive index homogeneity, (3) isotropic optical properties, (4) small strain birefringence, (5) very low coefficient of thermal expansion, (6) very high thermal stability, (7) high chemical and environmental durability, (8) small number of bubbles or inclusions, (9) ability to be polished to high standards, and (10) index of refraction match with silica core fiber optics. There are four primary methods of manufacturing silica optics. The first two processes involve melting naturally occurring quartz crystals at high temperatures. The resulting materials are fused quartz. Deficiencies of fused quartz optics can include substantial amounts of cation impurities (Type I), hydroxyl impurities (Type II), inhomogeneities, seeds, bubbles, inclusions, and microcrystallites. Types III and IV are synthetic fused silica. The cation impurity content of fused silica optics is substantially lower than fused quartz optics because of the higher purity of the raw materials. An important consequence of the elimination of impurities is the improvement of transmission throughout the optical spectrum. Elimination of ‘OH’ radicals from gel-silica optics also results in elimination of absorption bands in the near infrared. A very low coefficient of thermal expansion (CTE) is an important physical characteristic of optical silica. Every optical component requires the design of a custom mold and adoption of the sol-gel process to meet the requirements of that design.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call