Fused Silica (IR Grade SiO2)

Fused silica is often used in near infrared systems performing in the 0.8-2.5µm spectral region. It is also frequently used at the popular 1.064µm Nd:YAG laser wavelength.

The material has high homogeneity and good transmission in the visible and near infrared spectral regions. Cost of the material ranges widely by type and purity. However the most common Fused Silica for infrared use is quite a bit more expensive than Silicon and slightly less expensive than Calcium Fluoride or ZnS Multi-spectral grade. Due to the materials inherently hard SiO2 amorphous structure, the material is not diamond turnable. Typical specifications for surface quality in the near infrared regions are a 40-20 scratch dig.


Property Specification
Transmission Range 0.25µm to 3.5µm
Density 2.202g/cm3
Thermal Expansion 5.5 x 10-7 /°C @ 20 to 320°C
Surface Finish Fused Silica polishes extremely well & polishes of 10-5, or 20-10 scratch-dig are achieved at extra costs respectively, mainly for UV & visible applications.
Surface Figure In the infrared, typical surface figure ranges from 1/4 wave to 2 waves @ 0.6328µm & are specified depending on the system performance requirements.
AR Coating Options Typical available infrared coatings are a BBAR from 0.8 – 2.5µm & an AR coating for 1.064µm wavelength.
Typical Applications Thermal imaging, Astronomical, Microlithography, Excimer laser applications, Nd:YAG laser applications.
Products Manufactured Lenses, Windows, Wedges, Optical Beamsplitters, Optical Filters, Prism.


Wavelength (µm)
Index of Refraction (n)


IR Fused Silica Typical Curve