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Optics-M produces lenses, windows, prisms, wedges and others optical components according to customers’ specifications and drawings out of optical glass.

N-BK7 is a Schott designation for the most common Borosilicate Crown glass used for a wide variety of visible applications. The basic data here is given for N-BK7. Full optical design data on N-BK7 and other glasses can be found by following the web links at the bottom of this page.

Product Data

Transmission Range 350nm to 2.5 μm
Refractive Index 1.51680 @ 587.5618 nm (Yellow Helium Line)
Reflection Loss 8.1% at 587.5618 nm (2 surfaces)
bsorption Coefficient --
Reststrahlen Peak --
dn/dT See Schott Table
dn/dμ = 0 --
Density 2.51
Melting Point 557°C (Transformation Temperature)
Thermal Conductivity 1.114 W m-1 K-1
Thermal Expansion 7.1 x 10-6 K-1
Hardness Knoop 610
Specific Heat Capacity 858 J Kg-1 K-1
Youngs Modulus (E) 82 GPa
Shear Modulus (G) n/a
Bulk Modulus (K) 34 GPa
Elastic Coefficients n/a
Apparent Elastic Limit 63.5MPa (9206psi)
Poisson Ratio 0.206
Solubility Insoluble in water
Molecular Weight n/a
Class/Structure Amorphous glass

Transmittance

Refractive Index

No = Ordinary Ray

µm No µm No µm No
0.365 1.53626 0.4047 1.53024 0.4358 1.52669
0.4800 1.52283 0.4861 1.52238 0.5461 1.51872
0.5876 1.51680 0.5893 1.51673 0.6328 1.51509
0.6438 1.51509 0.6563 1.5143 0.7065 1.51289
0.852 1.50981 1.0140 1.50731 1.0600 1.50669
1.5296 1.50094 1.9700 1.49500 2.3254 1.48929