Optical 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.
 
Product Data -----------------------------------------------------
 
Transmission Range : 0.12 to 7 μm (1)
Refractive Index : No 1.413 at 0.22 μm (4)
Reflection Loss : 5.7% at 0.22 μm (2 surfaces)
Absorption Coefficient : 40 x 10-3 cm-1 at 2.7 μm
Reststrahlen Peak : 20 μm (1)
dn/dT : 2.3 (para) 1.7 (perp) at 0.4 μm (1)
dn/dμ = 0 : 1.4 μm
Density : 3.18g/cc
Melting Point : 1255°C
Thermal Conductivity : 21 (para) 33.6 (perp) W m-1 K-1 at 300K (3)
Thermal Expansion : 13.7 (para) 8.9 (perp) x 10-6 /K (1)
Hardness : Knoop 415
Specific Heat Capacity : 1003 J Kg m-1 K-1
Dielectric Constant : 4.87 (para) 5.45 (perp) at 1MHz (1)
Youngs Modulus (E) : 138 GPa (2)
Shear Modulus (G) : 54.66GPa (2)
Bulk Modulus (K) : 101.32 GPa (2)
Elastic Coefficients : C11=140 C12=89 C44=57 C13=63 C66=96 (2)
Apparent Elastic Limit : 49.6 GPa (7200 psi)
Poisson Ratio : 0.276 (2)
Solubility : 0.0002g/100g water
Molecular Weight : 62.32
Class/Structure : Tetragonal, can cleave on c-axis
 
Refractive Index and Optical Transmittance curve----
Refractive Index(No=Ordinary Ray):
µm    No µm    No µm    No
2.058    4.102 2.153    4.0919 2.313    4.0786
2.437    4.0708 2.577    4.0609 2.714    4.0562
2.998    4.0452 3.303    4.0369 4.258    4.0216
4.866    4.017 6.238    4.0094 8.660    4.0043
9.720    4.0034 11.04    4.0026 12.00    4.0023
13.02    4.0021
Optical Transmittance Curve of BK7 (Reference Data):
optical-glass-nbk7-b270-and-others Transmittance
 
Special properties of BK7-----------------------------------

Typeical application:Astronomical, Thermal Imaging

Products manufactured:Lenses, Windows, Wedges, Prism, Beam Splitters, Filters.

Surface finish:BK-7 polishes extremely well and polishes of 10-5, or 20-10 scratch-dig are achieved at extra costs respectively, mainly for UV and visible applications.

Surface figure:Surface figure of 1/10 wave to 1/4 wave @0.6328μm are specified mostly on lenses for ultraviolet and visible use.

AR coating options:AR @ 0.8-2.5μm, AR @ 1.064, AR @ Visible W.L.
Product Notes:------------ --------------------------------------

These two optical glasses are selected as representative of typical Crown Glass formulations in common use. There are many other glasses including higher density and higher dispersion glasses. Link below to access a larger range.

WEBLINKS:
Schott Glass Catalogue - Data on all Schott Glass types.

Data provided is extracted from our technical handbook of materials. While every attempt has been made to verify the source of the information, ultiQuest Technology accept no responsibility for accuracy of data

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