What is optical DLC coating

In this article, we will share what is DLC (Diamond-Like Carbon) COATING, DLC coating function, and its application.

A lens with light coming out of it

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DLC (Diamond-Like Carbon) coating is a type of coating that exhibits some of the unique properties of diamond. It is used in a variety of applications to reduce friction, improve wear resistance, and protect against corrosion. DLC coatings are made up of a carbon structure that includes both sp^3 (diamond) and sp^2 (graphite) bonds, giving it characteristics similar to those of diamond, such as high hardness and low friction, while also providing the flexibility and toughness of graphite.

  • High Optical Transparency: DLC coatings are highly transparent in the infrared (IR) and visible light spectrum, which makes them ideal for optical applications, including lenses and optical fibers.
  • Low Refractive Index: The refractive index of the coatings is lower than that of many other coatings, which reduces the amount of light reflected and allows for more light to pass through the material.
  • Anti-Reflective (AR) Capability: By adjusting the thickness and composition of the DLC coating, it can be engineered to reduce reflections from surfaces, enhancing the transmission of light through optical components.
  • UV Resistance: the coatings are resistant to degradation by ultraviolet (UV) light, making them suitable for outdoor applications where UV exposure is a concern.

Electrical Properties

  • Insulating Properties: Pure coatings are electrical insulators, due to the sp^3 bonding of carbon atoms similar to diamond. This makes them suitable for protecting sensitive electronic components.
  • Semi-Conductive Properties: By doping DLC coatings with elements like silicon or boron, their electrical conductivity can be increased, making them useful in semiconductor applications.

There are several types of DLC coatings, which can vary based on their structure and the specific ratio of sp^3 to sp^2 bonds. These variations can include:

  • Pure : Consisting entirely of carbon.
  • Metal-doped: Incorporates metals like silicon, titanium, or silver to improve certain properties, such as adhesion to substrates or wear resistance.
  • Hydrogenated (a-C:H or DLC-H): Contains hydrogen, which can affect its mechanical properties and stability.

DLC coatings are applied using various physical and chemical vapor deposition processes, such as PECVD (Plasma Enhanced Chemical Vapor Deposition) and PVD (Physical Vapor Deposition). The choice of process and the specific type of DLC coating used depends on the application and the desired properties of the finished product.

Applications of DLC coatings are widespread and include cutting tools, engine components, medical instruments, and electronic devices. The use of the coatings can significantly extend the lifespan of components, reduce maintenance costs, and enhance the performance of the products in which they are used.

Shape Optics have the optical and DLC coating  expertise to ensure our customers choose the best components for the entire optical coating based on application and use environment. Give us a call to talk to one of our engineers and learn how.

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