ISO 9001 - AS 9100 - ITAR Standard & Custom Optical Filters and Coatings

diamond like carbon DLC optical filters


Diamond-like Carbon (DLC) is a hard durable coating with useful properties as an infrared optical coating. The coating is a mix of graphitic and diamond forms of Carbon. As a result, the film structure has no long range order and cannot be fractured. The presence of the diamond-like form imparts a hardness that cannot be matched by other coating materials typically used in the design of infrared optical coatings. The refractive index of DLC is about 2.0 and this makes it an ideal coating material for use as an anti-reflection coating when applied to higher index infrared optical materials. The infrared materials Germanium and Silicon have high refractive indices of 4.0 and 3.4 respectively.

Typically, the higher index materials are used as the first lens of an infrared lens assembly due to the high refractive power. The first lens is subjected to a harsher environment and the increased durability afforded by the DLC coating greatly enhances the protection of outer facing lens surfaces. DLC is a chemically inert nonporous coating with the high hardness associated with diamond. Therefore, it will easily survive exposure to harsh environmental testing such as 10-day humidity, acidified salt fog and severe abrasion. There is even a sand slurry wiper blade test specific to DLC that demonstrates its’ superior abrasion resistance compared to other infrared coating materials.

Andover Corp can offer DLC as an option on Germanium or Silicon lenses and windows when durability and optical performance is desired.


  • Film structure has no long range order and cannot be fractured
  • Imparts a hardness that cannot be matched
  • Easily survives exposure to harsh environmental testing