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IR Air-Spaced Achromatic Doublets Optimized for 1.65 - 3.0 µm
These AR-coated, air-spaced achromatic doublet lenses provide excellent transmission in the 1.65 - 3.0 µm range (transmission can be seen in the graphs below). They incorporate two AR-coated lenses, one with a calcium fluoride substrate and another with an Infrasil 302 substrate.
Each achromatic doublet on this page has three design wavelengths: 1.65 µm, 2.3 µm, and 3.0 µm. By optimizing the design for these three wavelengths, the focal shift across the 1.65 - 3.0 µm range will be minimized, providing excellent on-axis performance. Note that since optical cement absorbs IR light, these doublets have an air-spaced design.
Thorlabs' IR achromatic doublets are pre-mounted in engraved Ø1" housings, making them easy to incorporate these optics into your setup. Each engraving includes the part number, AR coating range, focal length, an arrow indicating the direction of light propagation to collimate a point source, and an infinity symbol denoting that this lens has an infinite conjugate ratio (i.e., if a diverging light source is placed one focal length away from the flat side of the lens, the light rays emerging from the curved side will be collimated).
Note: We do not recommend disassembly of these lenses, as this may affect performance.