Anti Reflective (AR)
Many coatings consist of transparent thin film structures with alternating layers of contrasting refractive index. Layer thicknesses are chosen to produce destructive interference in the beams reflected from the interfaces, and constructive interference in the corresponding transmitted beams. This makes the structure's performance change with wavelength and incident angle, so that color effects often appear at oblique angles. A wavelength range must be specified when designing or ordering such coatings, but good performance can often be achieved for a relatively wide range of infrared, visible, or UV.
- Single-layer interference
The simplest interference AR coating consists of a single quarter-wave layer of transparent material whose refractive index is the square root of the substrate's refractive index; this, theoretically, gives zero reflectance at the center wavelength and decreased reflectance for wavelengths in a broad band around the center.
- Multi-layer interference
By using alternating layers of a low-index material like silica and a higher-index material it is possible to obtain reflective as low as 0.1% at a single wavelength. Coatings that give very low reflectivity over a broad band can also be made, although these are complex and relatively expensive. Optical coatings can also be made with special characteristics, such as near-zero reflectance at multiple wavelengths.
Our AR coating offers the best optical characteristics because it’s designed to have a bottom reflectance at 550nm to which the human eye is most sensitive.