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Germanium (Ge) is a relatively hard, high-density, IR transmitting material that blocks UV and VIS wavelengths but allows IR from 2µm. Germanium has the highest refractive index of commonly available IR-transmitters and has low optical dispersion. This makes it desirable in aspects of lens design where its refractive index allows otherwise impossible specifications to be built. AR coating is recommended.

Germanium transmits over 45% between 2-14μm up to 45⁰C but transmission degrades slowly at 100⁰C then more rapidly above 200⁰C. Exposure to higher temperatures can lead to catastrophic failure in the material so Germanium is unsuitable for use in these conditions. Additionally, its relatively high density should be considered where weight is an issue. Germanium has a hardness of HK780, slightly higher than GaAs with which it shares similar mechanical properties.

Typical applications for Germanium include thermal imaging where the material can be used as a front optic while its index of refraction makes Germanium useful for wide-angle lenses and microscopes. Additionally, Germanium components can be used for FLIR (Forward Looking Infrared) and FTIR (Fourier Transformed Infrared) spectroscopy systems, alongside other analytical instruments.

Knight Optical stock a range of Germanium Windows DLC/AR coated for 7-12 µm, we can also offer custom Germanium windows to your specific requirement. Other Germanium components we can also offer are, Germanium lenses, Germanium prisms, and Germanium blanks to your specification for a range of applications. Every component is individually tested by our highly skilled technicians in our state of the art metrology lab to ensure all components meet our high quality standards


Surface Quality:

± 0.2mm
± 0.2mm
1/10th wave at 10.6 micron (uncoated parts not toleranced)
<60-40 scratch/dig
5 arcmin
Avg.T%>85% @7-14 micron*
Avg.T%>85% @3-12 micron*

*as measured on 1mmthk substrate

Mounting into cells.
Edging down to smaller sizes.

Uncoated material



34 Items

Name Diameter (mm) Length (mm) Width (mm) Thickness (mm) Coating Coated Sides Material Price Buy
wge1005 10 0.5 Uncoated None Germanium
WGE1000 10 2 Uncoated None Germanium
wge1202 12 2 Uncoated None Germanium
WGE1212 pdf 12.5 1 AR/AR 3-12um Both Germanium
WGE1211 pdf 12.5 1 AR/DLC 7-14um Both Germanium
WGE1215 12.7 1.5 AR/AR 3-8um Both Germanium
wge1601 16 1 Uncoated None Germanium
wge1803 18 3 Uncoated None Germanium
wge1902 19 2 Uncoated None Germanium
wge2425 24 2.5 Uncoated None Germanium
wge2505 25 0.5 Uncoated None Germanium
WGE2500 25 1 Uncoated None Germanium
WGE2542 pdf 25 1 AR/AR 3-12um Both Germanium
WGE2511 pdf 25 1 AR/DLC 7-14um Both Germanium
WGE2501 25 2 Uncoated None Germanium
WGE2544 pdf 25 3 AR/AR 3-12um Both Germanium
WGE2533 pdf 25 3 AR/DLC 7-14um Both Germanium
wge2504 25 4 Uncoated None Germanium
WGE2502 25.4 1 Uncoated None Germanium
WGE2522 25.4 2 Uncoated None Germanium
WGE3005 30 0.5 Uncoated None Germanium
WGE3001 30 1 Uncoated None Germanium
WGE3002 30 2 Uncoated None Germanium
WGE3033 pdf 30 3 AR/DLC 7-14um Both Germanium
WGE3200 32 3 Uncoated None Germanium
WGE5012 pdf 50 1 AR/AR 3-12um Both Germanium
WGE5014 pdf 50 3 AR/AR 3-12um Both Germanium
WGE5033 pdf 50 3 AR/DLC 7-14um Both Germanium
WGE5011 pdf 50 10 AR/DLC 7-14um Both Germanium
WGE7533 pdf 75 3 AR/DLC 7-14um Both Germanium
WGE10011 pdf 100 10 AR/DLC 7-14um Both Germanium
WGE1311 13 11 0.3 Uncoated None Germanium
WGE2911 29.5 11.7 1 Uncoated None Germanium
WGE2523 25 23.5 1 Uncoated None Germanium

34 Items


Germanium Windows

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