BIOTAIN CRYSTAL > Substrate Materials > Optical windows > Product Information > Next :Silicon(Si) window

Germanium(Ge) window

Germanium(Ge) window

Germanium(Ge) optical window


 Single crystal of Germanium(Ge)

Other Names

Germanium window substrate, Ge window, Germanium IR window

Crystal structure


Applicable wave band

2μm ~ 14μm

Melting Point


Operating temperature

Crystal properties

Orientation: <111>
Conductivity type: N-type
Resistivity: 5-40 Ohm-cm


5.33 g/cc

Refractive index

4.0026 at 11 μm

Absorption coefficient

≤0.027 /cm at 10.6μm

Thermal conductivity

58.61 W/mK at 293K

Knoop Hardness


Thermal expansion coefficient

6.2×10-6/℃ at 298K

Maximum size

 Diameter 250mm (Single crystal)

Material Standard Size Surface quality
Germanium(Ge) window φ10.0mm x 1.0mm
φ25mm x 1.0mm
φ25.4mm x 3.0mm
φ25.4mm x 5.0mm
φ50mm x 1.0mm
φ50.8mm x 3.0mm
12.7 x 12.7 x 3.0mm
25.4 x 25.4 x 3.0mm
Or others
Polishing:             Double side optical polished or Epi-polished
Roughness:          Ra<1.5nm or Ra 5~10nm, Ra<0.5nm, 
Size Tolerance:          +/-0.1mm
Thickness Tolerance: +/-0.1mm or +/-0.05mm
Parallelism:           1 minute, 30 seconds, 5 seconds or higher
Surface Finish:      60-40, 40-20, 20-10 (scratch-dig)
Surface Figure:      1/2λ, 1/4λ or higher
Chamfer:                0.25mm × 45°
Coating:                 Upon requirements

Silicon windows and Germanium windows are the most commonly used Infrared(IR) windows. The best working wavelength of Silicon windows is 3-5um, and the best working wavelength of Germanium windows is 2-14um. It is one of the best substrate materials for filters.

Germanium has good thermal conductivity and a high epinuclear hardness and strength, it is often used in Infrared systems that require higher strength. Due to its high refractive index, an Antireflection(AR) coating is usually required to improve the transparency of Germanium windows, its commonly used wave bands are: 3~12um or 8~12um. The transmission properties of Germanium are extremely sensitive to temperature changes. The higher the temperature and the lower the transmittance. The best Operating temperature of Ge window is <100 ℃.

Germanium windows have higher hardness than Magnesium fluoride(MgF2) windows and can be used in the field of optoelectronics, Infrared thermal imaging cameras, Infrared laser systems, Infrared optical instruments, Infrared optics, etc.

We can customize different size and thickness of Germanium(Ge) optical window upon requirements, such as Germanium(Ge) round wafer, Square substrate and Cylinder, or Punch holes and other shapes.
Send Inquiry Online

For more information, please feel free to send us an Online Inquiry or Email us.

Contact Us

  • Tel: (+86) 1506 0796 451
  • Fax: (+86) 0597 2212602
  • Email:
  • Work Time ( GMT +8 ):
  •    9 AM ~ 6 PM, Monday to Friday
  • Main office: A7, No. 501, Denggaoxi Road, Xipi street, Xinluo District, Longyan, Fujian, China