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IR Neutral Density Filters

  • Reflection type IR ND filters
  • Germanium (Ge) substrates and metal alloy coating
  • Wide wavelength spectra 2.2μm to 15μm
  • Custom Optical Density (OD)
  • Custom Diameter range optional
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Substrates Germanium Diameter Range Custom
Transmission 10%, 20% or custom Aperture BBAR Coating on back surface S2 Optional
Dimension Tolerance ±0.2mm Clear Aperture +/-0.2mm90% of outside dimension
Surface Quality 80/50 S/D Flatness 2-4 waves per 25mm
Parallelism 3-5 arc minutes Mechanical Unmounted

Metallic-coated infrared neutral density filters (IR ND filters) obtain their optical density from a metal alloy coating on a substrate determined by the wavelength region of interest. Unlike the all-dielectric or absorption type, the metallic type ND filter employs a combination of absorption and reflection to reduce the intensity of light.

Infrared Neutral Density Filters are designed to attenuate radiation over a wide spectral range. These filters are coated on germanium substrates. The ND coating is optimized at 2.2 microns and can be used out to 15 microns.


1. Transmission of IR ND filters (Germanium, T=10%, BBAR coating on back surface S2)


2. Transmission of IR ND filters (Germanium, T=10%, No BBAR coating on back surface S2)