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25.4mm Dia., 5mm Thick, Uncoated, ISP Optics Germanium (Ge) Window | GE-W-25-5

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Stock #24-557 3-4 days
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Protective as needed
Clear Aperture (%):
Clear Aperture CA (mm):
Diameter (mm):
25.40 +0.00/-0.13
Thickness (mm):
5.00 ±0.13
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
Surface Flatness (P-V):
λ/10 @ 10.6μm
Surface Quality:
Protective Window
Wavelength Range (nm):
2000 - 14000
Young's Modulus (GPa):
Model Number:

Regulatory Compliance

RoHS 2015:
Certificate of Conformance:

Product Family Description

  • Minimal Chromatic Aberration Due to Low Dispersion
  • Uncoated Transmission from 2 – 16µm
  • Available with BBAR or DLC Coating for 8 – 12µm
  • Due to material supply chain disruptions with germanium, there may be increased lead times and price changes on our germanium products. For more information, please contact our customer service team.

ISP Optics Germanium (Ge) Windows provide transmission and low absorption through the Long-Wave Infrared (LWIR) spectrum, making it useful for thermal imaging applications. Germanium features a Knoop Hardness of 780, making it ideal for infrared applications requiring rugged optics. These windows are available uncoated, Broadband Anti-Reflection (BBAR) coated for 8 – 12µm, or Diamond-Like Carbon (DLC) coated for 8 – 12µm. ISP Optics Germanium Windows are ideal for integration into thermal imaging systems, especially those that require rugged optics. 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.