Germanium (Ge) Prism

Material: Germanium
Dimension: 60.00mm
Thickness: 10.00mm
Tolerance : +/-0.10mm

Germanium (Ge) prism 

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.


VY Optical supply a range of quality Ge prisms either from stock or bespoke custom made 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.

Due to its high index of refraction, an anti-reflection coating is recommended on these ge windows for sufficient transmission. 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. High density (5.33 g/cm3) of germanium 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.

Property of Germanium

  • Clear Aperture (%): 90.00
  • Dimensional Tolerance (mm): +0.0/-0.1
  • Coefficient of Thermal Expansion CTE (10-6/°C): 6.1
  • Density (g/cm3): 5.33
  • Index of Refraction nd: 4.002 @ 11µm
  • Knoop Hardness (kg/mm2): 780.00
  • Parallelism (arcmin): <1
  • Poisson's Ratio: 0.28
  • Substrate: Germanium (Ge)
  • Surface Quality: 60-40
  • Thickness Tolerance (mm): ±0.1

VY Optics also supply precision windows fabricated from several other substrates for use in a large variety of laser and industrial applications. 



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