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Germanium (Ge)

Spectroscopic and thermo-mechanical properties

Transmission Range 1.8 to 23 μm
Refractive Index 4.0026 at 11 μm
Reflection Loss 53% at 11 μm (Two surfaces)
Absorption Coefficient <0.027 cm-1 @ 10.6 μm
Reststrahlen Peak n/a
dn/dT 396 x 10-6 /°C
dn/dμ = 0 Almost constant
Density 5.33 g/cm3
Melting Point 936 °C
Thermal Conductivity 58.61 W m-1 K-1 at 298K
Thermal Expansion 6.1 x 10-6 /°C at 273K
Hardness Knoop 780
Specific Heat Capacity 310 J Kg-1 K-1
Dielectric Constant 16.6 at 9.37 GHz at 300K
Youngs Modulus (E) 102.7 GPa
Shear Modulus (G) 67 GPa
Bulk Modulus (K) 77.2 GPa
Solubility Insoluble in water
Molecular Weight 72.59
Class/Structure Cubic Diamond, Fd3m

Standard specifications

Orientation ---
Clear aperture >90%
Face dimensions tolerance +0/-0,1 mm
Length tolerance ±0,1 mm
Parallelism error <10 arcsec
Perpendicularity error <10 arcmin
Protective chamfers <0,1 mm at 45˚
Surface quality 40-20 S-D
Surface flatness <λ/8@632,8 nm
Wavefront distortion λ/4@632,8 nm
Coatings Custom
Laser induced damage threshold ---
Mount Unmounted