Manufacturers of optical coatings and components

An uncoated piece of optical crown glass (left) verses a piece of optical crown glass coated on one side with an antireflection coating (right), viewed at approximately 40^° angle of incidence.

When light (or for that matter any electromagnetic radiation) is incident upon the boundary between two media, some of the energy is reflected and some undergoes refraction and is transmitted.  There are several physical laws that govern the direction, amplitude, and phase of the reflected electromagnetic energy, but if one of the media is air, which has an index of refraction close to 1, then at normal incidence (the light propagates perpendicular to the surface of the glass) the reflectance for each surface is given by:

                            R = [(n-1)/(n+1)]²

where n is the index of refraction of the glass.

For glass with an index of refraction of 1.5 and negligible absorption, approximately 92% of the light will be transmitted though the glass and approximately 8% will be reflected (4% from each glass/air surface).

In multi-element systems, losing 4% of the incident energy at each surface can result in a significant overall loss of energy.  For example, the total loss for ten common glass optics (n = 1.5) is over 60%. Optics with higher indices of refraction will suffer even larger reflection losses.  Losses are also greater at higher angles of incidence.  To prevent reflection losses, anti-reflection coatings that significantly reduce the fraction of incident energy reflected from each surface must be applied to each surface.

Anti-reflection thin film coatings work by creating additional interfaces and tightly controlling the phase of the reflected energy such that the reflected waves from all interfaces nearly cancel one another out.  This results in very low surface reflectance. 

NTFL manufactures a wide range of anti-reflection coatings.  For more information concerning general types of antireflection (AR) coatings such as single layer anti-reflection (SLAR), V-coat (VAR), and broad band anti-reflection (BBAR) coatings, choose the appropriate navigation button above.

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