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TECHSPEC® components are designed, specified, or manufactured by Edmund Optics. Learn More

40mm Dia. x 4mm Thick, 8-12μm AR Coated, Ge Window

Germanium (Ge) Windows

Germanium (Ge) Windows

Stock #63-215
Qty 1-10
Qty 11+
Volume Pricing
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Protective as needed
Clear Aperture (%):
Clear Aperture CA (mm):
Diameter (mm):
40.00 +0.0/-0.1
Thickness (mm):
4.00 ±0.1
BBAR (8000-12000nm)
Coating Specification:
Ravg <3.0% @ 8 - 12μm
Coefficient of Thermal Expansion CTE (10-6/°C):
Density (g/cm3):
Fine Ground
Index of Refraction nd:
4.002 @ 11µm
Knoop Hardness (kg/mm2):
Parallelism (arcmin):
Poisson's Ratio:
Substrate: Many glass manufacturers offer the same material characteristics under different trade names. Learn More
Germanium (Ge)
Surface Flatness:
λ/10 @ 10.6μm
Surface Quality:
Protective Window
Wavelength Range (nm):
8000 - 12000
Young's Modulus (GPa):

Regulatory Compliance

RoHS 2015:
Reach 223:

Product Family Description

  • Uncoated or with AR Coatings Designed for a Variety of IR Ranges
  • Minimal Chromatic Aberration Due to Low Dispersion
  • Ideal for Infrared Applications Requiring Rugged Optics
  • DLC Coated Germanium Windows are also Available

TECHSPEC® Germanium (Ge) Windows are available off-the-shelf with three anti-reflection coating options: 3 - 5μm for mid-infrared applications, 3 - 12μm for broadband multispectral applications, or 8 - 12μm for thermal imaging applications. Due to its high index of refraction (around 4.0 from 2 - 14μm), an anti-reflection coating is recommended on these germanium windows for sufficient transmission in the region of interest. Germanium is subject to thermal runaway, meaning that the transmission decreases as temperature increases. As such, these germanium windows should be used at temperatures below 100°C. Germanium’s high density (5.33 g/cm3) should be considered when designing for weight-sensitive systems. The Knoop Hardness of germanium (780) is approximately twice that of magnesium fluoride, making it ideal for infrared applications requiring rugged optics.

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