NDUV20A In Stock

The NDUV20A by ThorLabs is a reflective neutral density (ND) filter that is made of UV fused silica substrates with nickel coatings on one side to provide a flat spectral response. With a diameter of Ø25 mm and a usable spectral range of 200 nm - 1200 nm, the NDUV20A is an excellent choice for a wide variety of applications.

The NDUV20A comes in a SM1 (1.035"-40)-threaded lens tube and is engraved with the part number, filter type, and optical density. The UV fused silica substrate of the filter has almost no fluorescence and high transmission, making it ideal for UV to the near IR applications. While the spectral range’s lower range is limited by the absorption of the substrate at 200 nm, UV fused silica provides up to 2.1 µm of superior transmission. The NDUV20A has an optical density (OD) of 2.0 and facilitates use in the UV thorough a specified design wavelength of 300 nm. If necessary, unscrewing the retaining ring that secures the filter with a compatible spanner wrench allows the filter to be removed easily from its housing.

The NDUV20A's metal coating is unprotected, which means it should be cleaned with only blown air and never touched, as contact could cause scratches. Although the filter is reflective, a portion of the incident light is absorbed through the nickel coating, limiting its use in low-power applications. Under normal conditions, nickel is aging-resistant, but it will oxidize at elevated temperatures. To avoid oxidation, it is recommended to use this filter at temperatures below 100 °C. For optimal performance, the NDUV20A should be used with light incident on the side with the nickel coating. This will allow for the occurrence of attenuation before etalon effects occur within the filter's substrate, resulting in the best possible performance.