Borosilicate Glass – BK7

Borosilicate glass is a type of glass that contains boron trioxide as a major component. It is known for its high thermal resistance and low coefficient of thermal expansion, which makes it a good choice for optical applications that require stable performance over a wide temperature range.

Borosilicate glass is commonly used in optics due to its high transmittance in the visible and near-infrared spectra. It is also relatively resistant to chemical attack, making it a good choice for applications where the optics may come into contact with harsh chemicals.

One of the most well-known brands of borosilicate glass used in optics is Pyrex, which is a registered trademark of Corning Incorporated. Pyrex is often used in lenses, mirrors, and other optical components due to its high quality and durability.

One of the disadvantages of borosilicate glass is that it is more difficult to manufacture than other types of glass, such as BK7. This can make it more expensive, particularly for large or complex optics. Additionally, borosilicate glass has a lower refractive index than other glasses, which can limit its usefulness in certain applications.

Overall, borosilicate glass is a versatile and reliable choice for many optical applications due to its thermal stability, chemical resistance, and high transmittance.