A Quick Explanation Of Optical Coatings For Glass And Semiconductors

In this modern world we are living in, a lot of the processes used to produce the things we use today have become more advanced. With this, one can be assured of a high-quality product at the end of the process used.

Among the many applications modern technology has perhaps the most popular one (aside from gadgets, of course) are optical coating technologies. Most of us are unfamiliar with this process or what it is per se, so it’s important to read more about optical coatings in this article.

What are optical coatings?

  • Layers of materials deposited on an optical component (glass, lens, mirror) to enhance the following properties:
  1. Transmission
  2. Reflection
  3. Polarization
  • Makes use of the Optical Coating Theory brought about by the Fresnel equations of refraction and reflection.

Coating technologies used

  1. Evaporative deposition
  • A vacuum is used to vaporize the source materials in the vacuum chamber using heating or electron-beam bombardment
  • Vapor condenses on the optical surface, and together with control of certain factors, results in the uniform optical coating with specific thickness
  • Plasma sputtering
  • Aka advanced plasma sputtering, magneton sputtering
  • Ions of plasma are accelerated to the source material, striking the loose ions on the target material
  • Ion beam sputtering
  • High-energy electric field is used to accelerate a beam of ions towards the target optic material
  • Atomic layer deposition
  • Works the same way as evaporative deposition, except that the source material for the vapor is gas instead of vaporizing a solid

Types of optical coatings

  1. Reflective coating
  • Used commonly in mirrors
  • A highly-reflective layer is deposited on the target optic
  • Common materials used: aluminium, silver, and gold
  • Anti-reflective coating
  • An optical coating type that maximizes the light passing through the optic
  • Commonly used in prescription lenses
  • Dielectric coating
  • Makes use of two materials with differing refractive indexes to be deposited on the target optic
  • Metal oxides are usually used for this coating (magnesium fluoride, calcium fluoride)
  • Commonly used in scientific optical instruments (lasers, microscopes, telescopes, interferometers) and consumer products (binoculars, spectacles, and photographic lenses)

For more information on these, you can always ask the optical engineer of a trustworthy company.