What are the advantages of BK7 (K9) beamsplitters?
(1) Wide band applicability
Suitable for visible (VIS) to near infrared (NIR) (350-2000 nm), ideal for most general purpose optical systems. Transmittance >90% in the 400-700 nm (visible) range (up to 99% with permeation enhancement coating).

(2) Low dispersion (high Abbe number)
Low dispersion, suitable for white light or broadband light source (such as LED, halogen lamps) to reduce the impact of color difference.

(3) Low cost, easy processing
Compared with fused silica, CaF₂ and other materials, BK7 is inexpensive and suitable for mass production. It is easy to cut, polish and coat, and has a high processing yield.

(4) Mechanical and environmental stability
Resistant to moisture, acid and alkali corrosion, suitable for general laboratory and industrial environments. Lower coefficient of thermal expansion, less influence of temperature change (but still not as good as fused silica).