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N-BK7 – high purity borosilicate glass

Very low absorption values

Maximum reflection

Own development department


Material: N-BK7 / S-BSL7

Borosilicate crown glass Glass used to manufacture low dispersion mirrors, lenses, windows, prisms and plane plates. There can be made from the following materials:

  • N-BK7 (Schott)
  • S-BSL7 (Ohara)


Borosilicate crown glasses for applications requiring low coefficient of expansion and good temperature resistance.



With optical coating optics are optimized for your application.

Gold with protection
A gold with protective coating is edeal for all appications in the infrared range. Including a protective ixide coating, the optics can be easily cleaned and prevents damage to the surface. This coating provides a reflection of R(avg) > 98 % in the IR from 1 - 20 µm.

Silver with protection
Silver with protection coated mirrors provide the highest reflectance of any metal from the visible to infrared spectral range. Including a protective oxide layer for easy cleaning and protection from oxidation, they are ideal for all broadband applications. Despite the protective coating, we recommend use in low humidity conditions to prevent tarnishing.

Aluminum with protection
A coating of aluminum with protection provides sufficient reflection for many optical systems. Including a protective oxide layer, it can be easily cleaned and it is protected from oxidation. Aluminum with protection provides a reflectance of R(avg) > 91% in the visible/NIR range of 0.4 - 2.0 µm and R(avg) > 94% in the range of 2- 20 µm.

Antireflective coatings
Uncoated N-BK7 lenses and windows reflect 4% of visible light on each side. Including an anti-reflective coating on both sides significantly increases performance and minimizes unwanted ghosting. AR coating we manufacture broadband or for one laser wavelength on request. Please contact us.

Rhodium / Platinum / Chrome
Rhodium or platinum coatings are used when extreme oxidation resistance is required. For example, most dental mirrors are rhodium coated. Both metals are also used as barrier coatings to prevent intermetallic diffusion. Chromium coatings are used as metallic neutral density filters as well as for the manufacture of calibration discs.

Do you need
Gold or silver mirror?

Here you can find our overview of optical mirrors
  • Density: 2,51 g/cm³
  • Knoop-hardness HK0,1/20: 610
  • Poisson’s ratio 0,206
  • Speed of sound 5720 m/s

Do you need more information about optics or components?

Please feel free to contact us!