Neutral Density Filters

Neutral density (ND) filters are used to attenuate the intensity of a light beam. They can be used to attenuate the intensity over a narrow range of wavelengths such as the emission of a laser or over a very broad spectrum such as the emission from a Tungsten-Halogen lamp. Two types of ND filters are commonly used in both OEM instrumentation and laboratory settings: Absorptive and Reflective-Absorptive (also referred to as Metallic).

Absorptive Neutral Density filters are fabricated from glass that has been colored in its molten state by the addition of a precise formulation of absorbing material. Glass "blanks" are ground and polished to provide not only an optical finish but to establish a thickness of the finished glass that will result in the desired degree of attenuation. Absorptive ND filters provide reasonably good neutrality over the visible spectrum.

Metallic (or Reflective-Absorptive) neutral density filters provide a relatively consistent degree of attenuation over a wide spectral band extending from the Ultraviolet (UV) to Short Wave Infrared (SWIR). This type of ND filter is manufactured by vacuum deposition of a thin-film coating onto glass or fused silica substrates.

Neutral Density filters can be found in almost any photonic application where attenuation of signal is desired.

To discuss your specific requirements, please call 508-528-4411 to speak directly to one of our Technical Sales Engineers, or email us at

While the vast majority of the neutral density filters that we manufacture are custom designed for OEM instrumentation, we also manufacture a selection of catalog products that are available for immediate delivery from inventory including both absorptive and metallic types at commonly used attenuation values.

Custom Specified Neutral Density
UV Fused Silica