Thorlabs FEL1000 Longpass Optical Filter

Thorlabs FEL1000 is an optical longpass filter manufactured by Thorlabs, designed to transmit wavelengths longer than approximately 1000 nm while blocking shorter wavelengths of light. It was part of Thorlabs’ FEL series of filters used in optical and photonics systems for spectral isolation, order sorting, stray‑light reduction, or other wavelength‑selective applications.

📌 Key Features (Typical for FEL1000)

• Filter Type: Longpass optical filter (soft‑coated) — passes wavelengths above ~1000 nm and blocks shorter wavelengths.

• Cut‑On Wavelength: ~1000 nm (the wavelength where transmission becomes significant).

• Diameter: ~1 inch (25.4 mm).

• Clear Aperture: ~21 mm.

• Substrate Material: Soda‑lime or equivalent optical glass.

• Construction: Immersed dielectric coatings (soft‑coated).

• Typical Use Cases: Photometry, Raman spectroscopy setups, astronomy, stray light suppression, and other optical systems where NIR isolation is needed.