Manufacturers of optical coatings and components

Newport Thin Film Laboratory fabricates optics from a number of optical materials.  There are hundreds of types of different optical materials.  To the optics designer, the most important parameters are the index of refraction and the dispersion (¶n/¶l).   However, there are other parameters, such as the internal transmittance, coefficient of thermal expansion, and resistance to staining that influence the choice of optical materials.

The most commonly used optical materials are optical crown glass,  borosilicate (e.g., Pyrex^®, Tempax^®, Borofloat^®), synthetic fused silica, Schott BK7^® and Schott Zerodur^®.

Crown glass:  A low index, commercial quality glass for which the index of refraction (1.52-1.53) and homogeneity is not tightly controlled.  Optical crown glass has a transmittance window of approximately 400-2000 nm and is suitable for many non-critical applications.

Borosilicate:  A low thermal expansion glass that is well suited for applications that involve high temperatures and/or thermal shock.  Borosilicate glass is also reasonably resistant to chemical attack.  Borosilicate glass has a transmittance window of approximately 400-2000 nm and an index of refraction of 1.47-1.48.

Synthetic Fused Silica:   An ideal optical material for many applications due to its extremely wide transmittance window (200-2000 nm), low coefficient of thermal expansion, and resistance to scratching and chemical attack.  Synthetic fused silica comes in various grades that differ in transmittance, UV band edge and bubble content.  Synthetic fused silica has much better optical quality than fused quartz, which is manufactured by crushing and melting natural crystalline quartz or silica sands.

BK7^®:   A widely used borosilicate crown glass that is used primarily for shaped optics such as lenses and prisms.  BK7 is a hard glass with excellent homogeneity and a low bubble and inclusion cross-section.  BK7 is relatively resistant to chemical attack and has a transmittance window of approximately 350-2200 nm.  BK7 has an index of refraction of 1.51947 at 532 nm.

Zerodur^®:   A glass-ceramic composite material with an extremely small coefficient of thermal expansion over a wide temperature range.  Zerodur is subjected to careful thermal processing during manufacture to create a composite composition that is approximately 75% crystalline and 25% amorphous.  Zerodur appears reasonably transparent, but due to the high crystalline composition, scattering at grain boundaries renders Zerodur unsuitable for transmissive optics.  As such, Zerodur is used almost exclusively for imaging mirrors.