Germanium (Ge)

Germanium is a high index material that is used to manufacture Attenuated Total reflection (ATR) prisms for spectroscopy. Its refractive index is such that germanium makes an effective natural 50% beamsplitter without the need for coatings. It is also used extensively as a substrate for production of optical filters. Germanium covers the whole of the 8-14 micron thermal band and is used in lens systems for thermal imaging. It can be AR coated with diamond producing an extremely tough front optic. Its transmission is very temperature sensitive, becoming opaque near 100 degrees C. Environment does not cause problems because Germanium is inert, mechanically rugged, and fairly hard. Germanium is grown by Czochralski pulling techniques. It is relatively expensive. The refractive index changes rapidly with temperature and material becomes opaque at all wavelengths a little above 293K. Maximum available size: 200 mm Dia x 50 mm Thk.

Crystaltechno Ltd. manufactures from Germanium Ge the following optics: blanks, windows, plates, polished domes, prisms, wedges and lenses. These products are used for infrared applications.

Spectral Transmittance of optical grade Ge Uncoated Polished Window thickness 5mm for range (2.5 - 25) microns.

Crystaltechno Ltd. offers the manufacturing of Ge optics (in detail please see Catalog):

Perhaps you will find required Germanium Ge optics at our stock, please see item Optical Crystals.


  Transmission Range   1.8 to 23 microns  
  Refractive Index   4.0026 at 11 microns  
  Reflection Loss   59.1% at 11 Вµm (2 surfaces)  
  Index of Absorption   1.3 x 10-3 cm-1 at 3.8 microns  
  dN/dT   396 x 10-6/°C  
  dN/dВµ = 0   R.I. almost constant  
  Density   5.33 g/cm3  
  Melting Point   936°C  
  Thermal Conductivity   58.61Wm-1K-1 at 293K  
  Thermal Expansion   6.1 x 10-6/°C at 298K  
  Hardness   Knoop 780  
  Specific Heat Capacity   310 J kg-1K-1  
  Dielectric Constant   16.6 at 9.37GHz at 300K  
  Young's Modulus (E)   102.7 GPa  
  Shear Modulus (G)   67 GPa  
  Bulk Modulus (K)   77.2 GPa  
  Elastic Coefficients   C11 = 129 C12 = 48.3 C44 = 67.1
89.6 MPa (13000psi)
  Elastic limit   89.6 MPa  
  Poisson Ratio   0.28  
  Solubility   Insoluble in water  
  Molecular Weight   72.59  
  Class/Structure   Cubic diamond, Fd3m  


  Wavelength, µm 2.06 2.15 2.44 2.58 3.00 3.42  
  Refractive Index 4.10 4.09 4.07 4.06 4.05 4.03  
  Wavelength, µm 4.36 6.24 8.66 9.72 11.04 13.02  
  Refractive Index 4.02 4.01 4.00 4.00 4.00 4.00  


Plano-Convex Lenses
Bi-Convex Lenses
Bi-Concave Lenses
Cylinder Lenses
Right Angle Prisms
ATR Prisms
ATR Hemispheres
Polished Domes

Ge germanium hemispheres - plano-convex lenses

Ge germanium ingot - high purity material

Ordering Info
  (c) Crystaltechno Ltd. 26 Bakinskih Komissarov 5, Moscow 119571, Russia
+7 (495) 234-5951, 234-5952, 780-7780
fax +7 (910) 485 67 82
Site suggestions: webmaster@crystaltechno.com