Germanium Windows

Germanium windows are optical components commonly used in various applications that require infrared (IR) transmission.

Germanium is a semiconductor material with a broad transmission range from 2-16μm, making it an ideal candidate for mid-wave infrared (MWIR) and long-wave infrared (LWIR) applications.

Its unique properties, such as durability and high optical clarity, make it an excellent choice for optical windows used in defense and aerospace, biomedical imaging, laser systems, and other infrared applications.

Lattice Materials specializes in precision manufacturing of germanium windows, while maintaining optical quality and reducing the absorption of infrared radiation.

Durability for Optimal Performance

Optical grade germanium is resistant to thermal and mechanical shock, making it suitable for IR applications that are subjected to variations in temperature and other mechanical stressors.

  • Due to its high mechanical strength, germanium can withstand harsh environmental conditions and reliably maintain performance over time.
  • Germanium has excellent thermal stability, allowing it to withstand temperature variations without significant deformation or degradation.


For example, germanium windows are used in thermal imaging systems to detect infrared radiation and enable remote thermal mapping.

Germanium IR windows or beamsplitters are also commonly used in infrared spectroscopy and for remote sensing applications that require detecting and analyzing infrared light.

While these can also be manufactured from other substrates with high transmission in the infrared spectrum, such as zinc selenide (ZnSe), magnesium fluoride (mgf2) calcium fluoride (CaF2), we prefer to use germanium because of its mechanical strength.

Crystal Structure: Diamond cubic

Density, g/cm3: 5.323
Mohs Hardness: 6.3

Index of Refraction @25: @3 microns, n = 4.0045

Absorption Coefficient @25, cm -1 @3 microns, a = 0.0047

Unmatched Optical Clarity

Germanium optics provide unmatched optical clarity, making them ideally suited for a wide range of optical systems.

  • Germanium has a high index of refraction, about 4.0 at a wavelength of 10 μm. Its refractive index allows it to bend light more effectively, making it ideal for manufacturing optical components like windows, lenses, and prisms that require strong light-bending capabilities for applications such as thermal imaging and infrared spectroscopy.
  • Germanium displays low absorption properties, allowing it to transmit infrared light with minimal energy loss. This property is useful in applications which require high sensitivity to transmit weak signals while maintaining image quality and fidelity, such as infrared cameras.


Germanium has low dispersion properties, allowing it to maintain the integrity of transmitted light, resulting in high optical clarity.

Atomic Density, atoms/cm3: 4.416 

Lattice Constant, nm @23℃: 0.565754

Surface Tension mN/m (=dyne/cm): 650

Poisson’s Ratio 125K-375K: 0.278

Melting Point : 937.4

Round or Rectangular Shapes up to 17.5″ (450 mm)

Polished to optical specifications better than 40/20 scratch/dig, 1/10th wave flatness and down to 10 Å RMS

Available as uncoated or coated

Custom thin film coatings, such as DLC and AR coating (antireflection coating) are available for increased durability.

*All specifications are dependent on part geometry.

Do you have a requirement for germanium windows? Send us your specific requirements, and our technical sales representatives will be in touch with you.

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