ABSTRACT
Light reflection and transmission at the planar surface of a dielectric material are determined by its refractive index. However, there are many circumstances under which the surface reflectance of light should be suppressed or enhanced. In this chapter, we describe how light can be controlled at the surfaces and interfaces of materials. Multilayer thin films are widely used to control the reflectance and transmittance of light. These films are usually deposited on glass, silicon or metal substrates by evaporation. It is possible to design multilayer films with special characteristics. Useful applications of such films include antireflection (AR) coatings, band-pass filters, and highly reflecting dielectric mirrors. Micro/nano-scale structures formed into the surface of a substrate can also play a role to suppress the surface reflectance. Unlike multilayered AR coatings, this structure is inherently broadband and works at a wide range of incidence angles. An alternative approach to reduce light reflection is to produce a porous layer on the surface or coat it with a thin film of graded refractive index.
