Atomic Layer Deposition
Optical coatings made by Atomic Layer Deposition possess a unique combination of properties. Like IBS coatings, each layer is stoichiometric and has a fully dense micro-structure. But ALD is also a conformal process, resembling conventional CVD, only with greater thickness control due to the nature of the film growth. ALD can be used to coat optics of any shape with metal oxide multilayer stacks or single-layer protective coatings. MLD has developed ALD systems to address the market need for conformal, highly precise and chemical resistant optical coatings.
Our Atomic Layer Deposited coatings may be applied to optics ranging from 5 mm to 800 mm in diameter. Single layer thickness varies less than ± 1% over the entire surface. Total loss is typically less than 50 ppm. Because ALD films are grown one monolayer at a time from the chemical reaction of gas-phase precursors, pin-hole free coverage is achieved with every film layer. Thus ALD interference coatings double as a barrier for certain environments.
MLD can also produce hybrid coatings, comprised of IBS layers in combination with ALD layers. These hybrid coatings are critical, for example, when fabricating high-energy laser mirrors or other precision optics which may be exposed to harsh chemical or corrosive environments.