Antireflective coatings and optical filters

Antireflective coatings (ARC) and optical filters (OF) are developed from classes of optical materials with their distinct functionalities of diminishing optical reflectance from a material surface and optical transmittance through a material, respectively, for a particular wavelength range of light. Among the optical materials, metal oxides serve as one of the major material sources for the fabrication of modern day ARC and OF, owing to their range of optical properties like refractive index, light reflectivity, absorptivity, and allied advantages of good mechanical strength, ease of adaptability, stability and along with the flexibility for other functional property additions. The adaptability of metal oxide optical material extends from matrix dispersion, thin-film coatings, patterned surfaces, and other morphological structures according to the application in demand, with a wide possibilities of fabrication techniques of bottom-up and top-down approaches. A comprehensive understanding of the working principle of different types of ARC and OF is thus necessary for the rational selection of materials and their fabrication methods. Hence, the major objective of this book chapter is to summarize different ARC and OF with their principle of operation, nature of activity, and material selection, focusing primarily on metal oxides as the optical material. Thus, it will serve as a quick guide to explore and research ARC and OF, which suffice for a wide extent of applications/industries such as healthcare, energy, architecture, astronomy, etc.