Germanium (GE)
 

 

 

Germanium (Ge) is used widely for lenses and windows in thermal imaging and FLIR applications. Its high index of refraction makes it of particular interest. The useful transmission range of Germanium windows is from 2 to 12 micron. Germanium is opaque in the visible.

Germanium has the property of thermal runaway, meaning that the transmission decreases as temperature increases. As such, Ge window should be used at temperatures below 100. The higher Knoop Hardness of Germanium (780) makes it ideal for IR applications requiring rugged optics. Germanium's high density (5.33g/cm3) should be considered when designing for weight-sensitive systems.

 

 

 

 

Material Properties

 

 

Material Type

N or P

Resistivity (Ohm/cm)

4-50

thermal conductivity (J/k .m .s)

58.61 @ 293K

Thremal Expansion Coefficients (1/C)

6.1x10-6 @298K

Density (g /cm-3)

5.33

Knoop Hardness (kg/mm2)

780

Absorption Coefficient

3x10-6 @ 10600nm

 

 

 

 

Capability

 

ATTRIBUTE

COMMERCIAL

HIGH PRECISION

End-faces Configuration

Flat

Dimension Tolerance

0.1mm

0.01mm

Surface Quality

40-20 scratch and dig

10-5 scratch and dig

Flatness

/4

/10

Parallelism

20"

2"

Perpedicularity

15'

5'

 

 

 

 

Specifications

 

 

Type

Polishing Area

Roughness

Thick plate

5x5mm

0.5nm

5x5 - 8x8mm

0.5nm

8x8 - 38mm

0.5nm

Prism

20x20mm

0.5nm

Thin plate

5x5mm

0.5nm

5x5 - 8x8mm

0.5nm

8x8 - 38mm

0.5nm

 

 

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