ND Filters: Unmounted, AR Coated for 350 - 700 nm
Features- Attenuate Light in the Visible (350 - 700 nm AR Coating)
- Optical Densities Ranging from 0.1 to 6.0
- Unmounted Ø1/2" and Ø25 mm Versions
- AR Coated to Reduce Back Reflections in an Optical System
- Ideal for Low-Power Applications (<1 Watt)
Thorlabs is pleased to offer its most popular unmounted absorptive neutral density filters with a broadband antireflection coating for the 350 - 700 nm range deposited on both surfaces. These filters are also available in mounted versions or with a broadband AR coating for the 650 - 1050 nm range. Please see the Selection Guide to the right for more information. The high-performance, multilayer broadband A coating deposited on each filter is designed to minimize surface reflections within the 350 - 700 nm range, thereby reducing the amount of stray light present. These coatings provide an average reflectivity that is less than 0.5% over the specified wavelength range when light is normally incident on the filter surface. Typical transmission data is shown by clicking on the graph icons in the tables below. Unlike metallic neutral density filters, each absorptive ND filter is fabricated from one member of a family of Schott glasses (see the Specs Tab for more information). Each Schott glass has a spectrally flat absorption coefficient. By varying the type of glass used and the thickness of that glass, we are able to produce our entire line of absorptive ND filters from just four types of Schott glass. See below for detailed information about the average transmission obtained with each of our AR-coated absorptive neutral density filters. The optical density, OD, is related to transmission, T, by the following equation: 
Choosing an ND filter with a higher optical density will translate to lower transmission and greater absorption of the incident light. For higher transmission and less absorption, a lower optical density would be appropriate. For lab safety, Thorlabs offers an extensive line of safety and blackout products that significantly reduces exposure to stray light.
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| Optical Density | Substrate | Substrate Thickness |
|---|
| 0.1 | NG11 | 0.6 mm | | 0.2 | NG11 | 1.4 mm | | 0.3 | NG11 | 2.3 mm | | 0.4 | NG4 | 0.7 mm | | 0.5 | NG4 | 0.9 mm | | 0.6 | NG4 | 1.1 mm | | 1.0 | NG4 | 1.9 mm | | 1.3 | NG4 | 2.5 mm | | 2.0 | NG9 | 1.4 mm | | 3.0 | NG9 | 2.1 mm | | 4.0 | NG9 | 2.8 mm | | 5.0 | NG9 | 3.6 mm | | 6.0 | NG1 | 1.5 mm |
| General Specifications |
|---|
| Diameter | 12.7 mm | 25.0 mm | | Diameter Tolerance | +0.0 / -0.25 mm | | Clear Aperture | >90% Outer Diameter | | Ravg (350 - 700 nm) | <0.5% | | Surface Flatness (@ 633 nm) | λ/4 | | Surface Quality | 40-20 Scratch-Dig | | Parallelism | 3 arcmin | 10 arcsec |
*Values given are typical. The actual thickness of each ND filter is dependent on the optical density of the lot of glass used to manufacture each lot of ND filters. |
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Additional Neutral Density Filters
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Unmounted Absorptive ND Filters (A Coated)
