Vitreous Silica is the generic term used to describe all types of silica glass, which manufacturers either refer to as Fused Silica or Synthetic Quartz. It is a noncrystalline glass form of silicon dioxide (quartz and sand) and is manufactured by melting naturally occurring crystalline silica, such as sand or rock crystal. It is unique from other types of glasses because it is manufactured using a single ingredient.

Fused silica, often referred to as synthetic quartz, is created by using high purity silica sand that has been manufactured from SiCL4, resulting in a transparent glass with an ultra-high purity and improved optical transmission. However, depending on the manufacturing process, water bubbles can get caught in the glass and result in a translucent appearance.

Fused silica glass has very high viscosity, which means that it can be formed, cooled, and annealed without crystallizing.

It is known for:

  • Extreme hardness
  • Resistance to high temperature
  • Extensive optical transmission in the ultraviolet spectrum, but some infrared fused silica glasses are available
  • Permeability
  • Low coefficient of thermal expansion (CTE)
  • High chemical purity
  • High corrosion resistance
  • Excellent electrical insulation qualities
  • Low refractive index variations
  • Low birefringence values
  • Large size capabilities
  • State-of-the-art homogeneity levels


Based upon customer demand, Sydor Optics offers Fused Silica made from the following substrate materials. Of course, if you don’t see a material you need, please contact a Sales Engineer, who will gladly discuss additional options that may be available.


Principle Uses of Fused Silica

Compared to other types of glass, fused silica is efficient at transmitting waves on the ultraviolet spectrum, so it is often used to make lenses and optics for the ultraviolet spectrum. Its low coefficient of thermal expansion makes it a great candidate for precision mirror substrates, and it is commonly used in semiconductor fabrication and laboratory equipment.

Other common applications are:

  • Windows for manned spacecraft, debris shields, etc.
  • Vacuum windows for high energy lasers
  • Precision instrumentation for medical and metrology
  • Projection mask for photolithography
  • First surface mirrors, such as those in telescopes
  • Laser windows
  • Glass wafers for photonic chips