K-BK7 by Sumita

Standard Rare Environmentally Friendly

K-BK7 by Sumita is a standard optical glass with a rare melt frequency. It transmits from 0.27 to 2.00 µm with an nd of 1.51633 and a Vd of 64.1. It has low thermal expansion (CTE of 6.3×10⁻⁶/K) and excellent chemical resistance.

Refractive Index vs Wavelength
Refractive Index Calculator
Valid range: 0.36–1.55 µm
dn/dλ vs Wavelength
dn/dλ Calculator
Valid range: 0.36–1.55 µm
Abbe Number Calculator
Transmission vs Wavelength
Transmission Calculator
Valid wavelength range: 0.270–2.000 µm
Optical Properties
Refractive Index (nd) 1.51633
Abbe Number (Vd) 64.1
Dispersion Formula Schott
Wavelength Range 0.36 — 1.55 µm
$$n(\lambda) = \sqrt{2.27058 - 0.0100594\,\lambda^2 + 0.010415\,\lambda^{-2} + 0.000288725\,\lambda^{-4} - 2.22145 \times 10^{-5}\,\lambda^{-6} + 1.42586 \times 10^{-6}\,\lambda^{-8}}$$
Thermal Properties
TCE -30/70°C (10-6/K) 6.3
TCE 100/300°C (10-6/K) 8.5
Thermal Conductivity (W/mK) —
Heat Capacity (J/gK) —
$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[6.84 \times 10^{-7} + 2(2.05 \times 10^{-8})\,\Delta T + 3(-1.55 \times 10^{-10})\,\Delta T^2 + \frac{4.18 \times 10^{-7} + 2(2.74 \times 10^{-10})\,\Delta T}{\lambda - 0.178}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$
Physical Properties
Density (g/cm³) 2.52
Relative Cost —
Mechanical Properties
Young's Modulus (GPa) —
Poisson's Ratio —
Knoop Hardness (kgf/mm²) —
Chemical Resistance
Climatic Resistance 1
Stain Resistance —
Acid Resistance 1
Alkali Resistance —
Phosphate Resistance —
Similar Glasses (Other Manufacturers)
Glass Manufacturer nd Vd Compare
L-BSL7 Ohara 1.51633 64.065129
D-K9 CDGM 1.51633 64.058952
D-K9GT CDGM 1.51633 64.058952
P-BK7 Schott 1.5164 64.06
S-BSL7 Ohara 1.51633 64.142022
BK7HT Schott 1.51633 64.14348
BSL7 Ohara 1.51633 64.150145
BK7 Schott 1.5168 64.167336
N-BK7 Schott 1.5168 64.17
N-BK7HT Schott 1.5168 64.17
Similar Glasses (Sumita)
Glass Manufacturer nd Vd Compare
BK7 Sumita 1.51633 64.1
P-BK40 Sumita 1.5176 63.5
K-PBK40 Sumita 1.5176 63.5
K-PBK40(M) Sumita 1.51497 63.3
BK1 Sumita 1.51009 63.4
K-PBK50(M) Sumita 1.52025 62.2
K-PBK50 Sumita 1.5225 62.3
K-PBK60 Sumita 1.5274 62.3
K-PBK60(M) Sumita 1.52483 62.0
BK3 Sumita 1.49831 65.1
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