Thin-Film optics is the study of optics that deals with thin structured layers of different material. In order to exhibit thin-film optics, the thickness of the layers of material must be on the order of the wavelengths of visible light. This is able 500nm. The layers have reflective properties due to light wave interference and the difference in refractive index between the layers, the air and the substrate. These effects alter the way the optic reflects and transmits light. It is called thin-film interference.
Thin film layers can be achieved through the deposition of one or more thin layers of material onto a substrate in manufacturing. Often this is achieved by using physical vapor deposition process or a chemical process. Thin films are used to create optical coating used in everyday life such as low emissivity panes of glass, anti-reflective coatings on glasses and mirrors.
Thin-film layers can be observed in the natural world. Their effects produce colors from soap bubbles and oil slicks. Thin-film layers also can be seen in the structural coloration of some animals. Iridescent colors that were once thought to result from planar laws turn out to result from more complex period photonic crystal structures in thin-film layers.