Thin Film Coating Material and vacuum coating processes use vacuum
technology to create a sub-atmospheric pressure environment and an
atomic or molecular condensable vapor source to deposit thin films and
coatings. The vapor source may be from a solid or liquid surface
(physical vapor deposition - PVD), or from a chemical vapor precursor
(chemical vapor deposition - CVD).
Thin-film optics is the branch of optics that deals with very thin
structured layers of different materials. 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 (about 500 nm). Layers at
this scale can have remarkable 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. This effect is observable in soap
bubbles and oil slicks.
More general periodic structures, not limited to planar layers, are
known as photonic crystals.
In manufacturing, thin film layers can be achieved through the
deposition of one or more thin layers of material onto a substrate
(usually glass), most often by a physical vapor deposition process
such as evaporative or sputter deposition, or a chemical process such
as chemical vapor deposition. These thin films are used to create
This process is used to create low-emissive panes of glass for houses
and cars, anti-reflective coatings on glasses, reflective baffles on
car headlights, and for high precision optical filters and mirrors.
Another application of these coatings is spatial filtering.
Thin-film layers are common in the natural world. Their effects
produce colors seen in soap bubbles and oil slicks, as well as in some
animals. For example, the light collecting tapetum lucidum of many
nocturnal species and the photophores of bioluminescent squid (e.g.
the Bobtail squid). In many cases, iridescent colors that were once
thought to result from planar layers, such as in opals, peacocks, and
the Blue Morpho butterfly, turn out to result from more complex
periodic photonic-crystal structures.