FB650-40 In Stock

The FB650-40 by ThorLabs is an outstanding bandpass filter that transmits a specific wavelength of light while rejecting unwanted radiation. The FB650-40 features a center wavelength of 650 ± 8 nm, making it one of the most efficient ways to transmit a well-defined wavelength band of light.

The FB650-40 is mounted in an unthreaded black anodized aluminum ring, which has an outer diameter of Ø1" and a maximum edge thickness sized at 6.3 mm. This ring boasts an arrow that displays the direction of the design transmission, making handling easier and limiting scattering through the magnification of blocking OD. The FB650-40 can be mounted into a variety of wheels and filter mounts, and a retaining ring is necessary in order to mount it into a lens tube that is threaded internally or filter mount because the filter mount is not threaded.

The FB650-40 is constructed with two reflecting layers that are placed apart by a spacer layer which is similar to the construction of a thin film Fabry-Perot interferometer. Low and high refractive index materials are layered alternately to form these reflecting stacks, which offer reflectance of more than 99.99%. The bandwidth and central wavelength of the FB650-40 can be altered through changing up the number of reflecting layers and/or varying the thickness of the spacer layer.

On either side of the bandpass region, the blocked light spectral range is narrow, even though the FB650-40 has very high transmission in the bandpass region. To make up for this, out-of-band radiation and reduction of overall transmission throughput can be eliminated through the use of a second blocking component. It is crucial to note that the FB650-40 is not recommended to be removed from its mount because of the glass layers that are held together with the mounting ring and epoxy. These glass layers are imperative to prevent atmosphere damage to the dielectric coating. Over time, exposure would result in the degradation of the filter’s transmission.