Germanium ( Ge )

Crystal properties   Germanium
Crystal Type: cubic, diamond structure
Transmission Range 1.8 ... 23 µm
Refractive Index 4.0034 @ 9.72 µm,
4.0028 @ 10.6 µm
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  Germanium ( Ge ) -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
α-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