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N-BK7 is a Schott borosilicate material used in optical applications from the visible to the NIR. Optical windows made of N-BK7 offer the following advantages:

  • Clear, uniform color
  • Nearly free of bubbles and inclusions
  • A high degree of purity and homogeneity
  • Excellent chemical and stain resistance
  • Superior transmission in the VIS to NIR spectrum
  • Low absorption and uniform transmission in the visible spectrum

Due to the above properties, N-BK7 can be used to fabricate both optical windows and optical mirrors. It is most often selected due to its relatively low cost, high index of refraction (1.51680 @ 587 nm, yellow helium line) and high transmission between 350nm – 2.5µm. For further technical information, view our N-BK7 Data Sheet.

While there are plenty of good reasons to choose N-BK7, it is a very temperature sensitive material and therefore not suitable for applications where it will be exposed to thermal shock. A good, but more expensive, alternative is fused silica which offers a lower coefficient of thermal expansion, a much greater resistance to thermal shock and a broader range of optimal transmission when compared to N-BK7. A good understanding of your application will help you decide if N-BK7 is the right choice.

Advanced Optics carries a wide range of N-BK7 in-house and has the ability to:

  • Fabricate custom shapes and sizes
  • Achieve parallelism of > 2 arc seconds
  • Drill holes, notch glass and provide custom bevels
  • Polish glass down to 3mm in diameter and 0.5mm thick
  • Modify and resurface customer supplied materials
  • Precision polish optics with non-standard aspect ratios
  • Provide broadband AR coatings for the visible spectrum as well as custom coatings

All of Advanced Optics optical windows are manufactured in the USA. Whether you require a single optic or production quantities, let Advanced Optics be your trusted partner – You can depend on our 100% outgoing inspection, on-time delivery and unmatched customer service at competitive prices.

BK7 Optical Windows

Have a question? Give us call and tell us about your project. (262) 548-1155