Optics

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
Density	5.32 g/cm³
Poisson’s Ratio	0.27
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