NDC-25C-2-B In Stock

The NDC-25C-2-B by ThorLabs is an unmounted, continuously variable neutral density filter that is designed for use in optical systems where back reflections are a concern. This filter features a 270° metallic ND coating on the front surface and an antireflection coating deposited on the back side, optimized for the 650 - 1050 nm wavelength range. The AR coating minimizes secondary reflections, making the NDC-25C-2-B an ideal choice for applications where back reflections could degrade performance.

The NDC-25C-2-B coating can be altered in a linear way by simply rotating it, and it consists of a UV fused silica glass substrate along with an Inconel metallic finish that spans a total of 270°. This design ensures a flat spectral response from the ultraviolet to the mid-infrared, making it an excellent option for a wide range of applications. The alloy Inconel is metallic and ensures that the near IR to the UV range produces a flat spectral response. The NDC-25C-2-B is a reflective ND filter that absorbs some of this produced incident light. As a result, it is recommended for use in low-power applications. It is important to note that unprotected metal coatings like this should have air that is blown across the surface in order to clean it. This is important because direct contact could result in the unprotected surface sustaining scratches.

The NDC-25C-2-B has an optical density ranging from 0.04 - 2.0, and the optical density increases linearly from the start of the coating. A higher optical density will result in lower transmission and greater reflection of the incident light, while a lower optical density will provide higher transmission and less reflection. For example, a filter with an OD of 2 will attenuate the beam to 1% of the incident power, resulting in a transmission value of 0.01. To ensure optimal performance, it's important to ensure light is incident on the Inconel coated side and the NDC-25C-2-B should be used at sub-100°C temperatures in order to deter oxidation. This filter boasts a circular design and is unmounted, providing ease of use and compatibility with a wide range of optical systems.