Research On Vacuum Coating Technology With Ion Assisted Deposition

In infrared optical system, most of infrared components must be coated with anti-reflection film to reduce light loss on surfaces. Coating technology of infrared anti-reflection film with high performance becomes a key process in infrared optical system. Infrared components not only must be provided with a good suitability of environment but also high optical characteristics because they are often used in adverse environment condition. Substrates with high refractivity are usually used in infrared spectrum, such as germanium (n=4.0). Infrared components will not be usable without anti-reflection film, since reflection loss of light on surface of material is very severe (for example, transmissivity of germanium is only 46% without anti-reflection film).It's a difficult problem to resolve the intensity difference of anti-reflection film of optical component caused by infrared germanium crystal in 8～12μm in domestic and abroad at present, because that usable coating material is very limited in infrared wave range, several current infrared coating material, such as ZnS, BaF₂, ZnSe are loose and easy to be humid.Vapor deposition process by electronic beam was usually used for infrared anti-reflection film coated on germanium substrate in domestic and abroad, but the adhesive force and anti-humid of film is not good, so that they are not used under adverse environment condition.In this paper, we will describe a coating broadband anti-reflection film on germanium surface by Ion Assisted Deposition technology with good quality and high reliability.