Standard substrates
Characteristics and transmission curves
are given for the most common substrate materials and more detailed information about
Fused Silica
N-BK7 and special glassses
Fluorides
Sapphire, YAG
Si, ZnSe and Ge
For some different materials we show the
Group Velocity Dispersion (GVD)
Reflection of an uncoated surface
Frequently asked questions
What type of Fused Silica (FS) do I need?
Most customers’ needs can be met with two standard materials, FS-UV and FS-IR.
They differ mainly at the absorption edge and the water and OH bands. FS-IR should normally be used when wavelengths above 2 μm or high- and partial-transmitting coatings in the range of 1200-1500 nm are used.
In the UV-VIS range different qualities for FS-UV are available, which mainly differ in the internal transmittance at the excimer wavelengths 193 nm and 248 nm. This also depends on the manufacturers and the raw material used. Therefore, LASEROPTIK has introduced its own classes for Fused Silica, an overview can be found here:
https://www.laseroptik.com/en/substrates/standard-substrates/fused-silica
What is the difference between fused silica and N-BK7?
Fused Silica (FS) is a synthetically produced quartz glass, N-BK7 a borosilicate crown glass. In addition to the refractive index, they differ mainly in material homogeneity, transmission range and thermal expansion coefficients. For high laser power and applications in the UV range, or above 1500 nm, FS should therefore always be used.
What is the difference between silicon (Si) and fused silica (SiO2) as substrate materials?
Silicon (Si) and Fused Silica (SiO2) have different crystal structures and completely different usable transmission ranges. Si is a semiconductor, SiO2 is an insulator.
Si is often used for mirrors in the FIR because of its very high thermal conductivity.
For laser optics Fused Silica is the most used glass material from UV to NIR. There is a wide range of different FS substrate materials available, varying in homogeneity, grades of laser induced fluorescence and content of bubbles, inclusions and OH.
https://www.laseroptik.com/en/substrates/standard-substrates/characteristics-and-transmission-curves
