FELH1250 In Stock

The FELH1250 by ThorLabs is a top-performing longpass filter that has proven to be a reliable solution for isolating spectral regions. The FELH1250's features and performance surpass those of other soft-coated edgepass filter counterparts. This longpass filter boasts an outer diameter of 25.0 with a Ø21.1 mm clear aperture, which is ideal for a variety of optical applications. In addition, this filter has an optical density (OD) in excess of 5 in the rejection region, providing greater blocking capability.

The transmission region of the FELH1250 has greater than 90% transmission, which is essential for optimizing optical system performance. This longpass filter features a durable dielectric coating that is hard-coated on the UV fused silica. The film construction is essentially a modified quarter-wave stack, which utilizes interference effects for spectral band isolation. The coating on this filter can withstand the normal cleaning and handling necessary when using high-quality optical components. Compared to standard filters, the coatings on the FELH1250 are more dense, allowing for only one substrate layer, which yields a filter that lasts longer and is more stable.

The FELH1250 housing consists of a aluminum ring with black anodized material that limits scattering thorough OD blocking enhancing. The ring makes handling easier and is labeled with an arrow indicating the design propagation direction. The FELH1250 can be mounted to a variety of wheels and filter mounts, but a retaining ring will be required to mount the filter into a compatible internally-threaded SM1 lens tube since the mount is not threaded. It is important to note that the risk of damaging the filter is high if it is removed from its mount, so it is not recommended.