Germanium (Ge)

Use Germanium's unique combination of high refractive index and excellent hardness to build durable, low-power imaging and laser systems with a minimum component count.

Germanium (Ge) is ideal for applications where ruggedness and durability are important, and Ge optics can withstand optical powers in the range of 50-100 watts. Its high refractive index enables its use as a beamsplitter without additional coating.

Germanium (Ge) Characteristics

Coherent supplies Ge substrates of up to 150 mm diameter, and carefully monitors 10.6 µm absorptivity to ensure that thermal runaway and fracture do not occur.

Ge Material Properties

Physical Properties

Young’s Modulus

100 GPa (12.04 x 106 psi)

Rupture Modulus

93 MPa (20,000 psi)

Knoop Hardness

692 kkg/mm²


5.32 g/cm³

Poisson’s Ratio


Thermal Properties

Thermal Conductivity @ 20° C

0.59 W/cm/°C

Specific Heat

0.31 J/g/°C

Linear Expansion Coefficient @ 20° C

5.7 x 10-6/°C

Optical Properties

Bulk Absorption @ 10.6 μm

<0.03 cm-1

Temperature Change of Refractive Index @ 10.6µm

408 x 10-6/°C