Germanium ( Ge )
Crystal properties | ![]() |
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Crystal Type: | cubic, diamond structure | |
Transmission Range | 1.8 ... 23 µm | |
Refractive Index | 4.0034 @ 9.72 µm, 4.0028 @ 10.6 µm |
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Reflective Loss | 52.9 % @ 10 µm | |
Density | 5.323 g/cm3 | |
Melting Point | 956, 959, 942, 938 °C | |
Molecular Weight | 72.59 | |
Thermal Conductivity | 58.61 W/(m K) | |
Specific Heat | 310 J/(kg K) @ 25 °C | |
Thermal Expansion | 5.5×10–6 / K, 6.1×10–6 / K | |
Hardness (Knoop) | 780 | |
Young’s Modulus | 102.7 <100>, 155.3 <111> GPa | |
Shear Modulus | 67 <100> GPa | |
Bulk Modulus | 77.2 GPa | |
Rupture Modulus | 93 MPa | |
Elastic Coefficient: | C11 = 129 / C12 = 48.3 / C44 = 67.1 GPa | |
Dielectric Constant | 16.6 @ f = 9.37 GHz | |
Solubility in Water | Insoluble | |
Application | Electronics lenses, band pass filters, thermography | |
Remarks | laser damage threshold: 2.9 ...3.3 GW / cm2 | |
Germanium substrates | ![]() |
List of Optical Crystals | ||||
Materials | Refractive Index | Transmission Range (mm) |
Density (g/cm³) |
Thermal Expansion Coefficient (10-6/K) |
BK7 glass | 1.5164 (588 nm) | 0.330 – 2.1 | 2.51 | 7.5 |
SF11 glass | 1.78472 (588 nm) | 0.370 – 2.5 | 4.74 | 6.8 |
F2 glass | 1.62004 (588 nm) | 0.420 – 2.0 | 3.61 | 8.2 |
Fused Silica | 1.4858 (308 nm) | 0.185 – 2.5 | 2.20 | 0.55 |
CaF2 | 1.399 (5.0 mm) | 0.170 – 7.8 | 3.18 | 18.85 |
BaF2 | 1.460 (3.0 um) | 0.15 – 12.0 | 4.88 | 18.4 |
Sapphire | 1.755 (1.0mm) | 0.180 – 4.5 | 3.98 | 8.4 |
Silicon | 3.4179 (10mm) | 1.200 – 7.0 | 2.33 | 4.15 |
Ge | 4.003 (10 mm) | 1.900 – 16 | 5.33 | 6.1 |
ZnSe | 2.40 (10 mm) | 0.630 – 18 | 5.27 | 7.8 |
ZnS | 2.2 (10mm) | 0.380 –14 | 4.09 | 6.5 |
LiF | 1.39 (500 nm) | 0.150 – 5.2 | 2.64 | 37 |
KBr | 1.526 (10 mm) | 0.280 – 22 | 2.75 | 43 |
MgF2 | no = 1.3836 ne = 1.3957 (405 nm) |
0.130 – 7.0 | 7.37 | a: 13.7 b: 8.48 |
YVO4 | no = 1.9500 ne = 2.1554 (1.3 mm) |
0.400 – 5.0 | 4.22 | a: 4.46 b: 11.37 |
Calcite | no = 1.6557 ne = 1.4852 (633 nm) |
0.210 – 2.3 | 2.75 | a: 24.39 b: 5.68 |
Quartz | no = 1.5427 ne = 1.5518 (633 nm) |
0.200 – 2.3 | 2.65 | 7.07 |
?-BBO | no = 1.6749 ne = 1.5555 (532 nm) |
0.190 – 3.5 | 3.85 | a: 4.0 c: 36 |
LiNbO3 | no = 2.2863 ne = 2.2027 (633 nm) |
0.370 – 4.5 | 4.64 | a: 16.7 c: 2.0 |