K9(Bk7)

borosilicate crown glass is used for windows, lenses, and prisms where transmission in the range 0.4µm to 1.4µm is desired. the refractive index varies from about 1.53 to 1.5 through this range. it is used for thermally non-critical applications.

 

property specification
transmission range 0.4µm to 2.5µm
density 2.51 g/cc
thermal expansion 7.1x10-6 /°k @ -30° + 70°c, & 8.3x10-6 /°k @ 20°c to 300°
surface finish bk-7 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 surface figure of 1/10 wave to 1/4 wave @ 0.6328µm are specified mostly on lenses for ultraviolet & visible use.
ar coating options ar @ 0.8-2.5µm, ar @ 1.064, ar @ visible wavelength.
typical applications astronomical, thermal imaging
products manufactured lenses, windows, wedges, prism, beamsplitters, filters.

 

wavelength (µm) index of refraction (n)
0.4047 1.530
0.4800 1.523
0.5461 1.519
0.6328 1.515
0.8521 1.510
1.0600 1.507
1.5300 1.501
1.9700 1.495
2.3250 1.489

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