An achromat is a compound lens made by cementing together two distinct optical glasses, typically a positive crown glass element and a negative flint glass element. The differing dispersions of the two materials cancel out chromatic aberration for two specific wavelengths. In laser labs, they are heavily used to focus multi-wavelength beams or broadband light to a tight spot without color fringing.
Heard on the job
Swap out that singlet for an achromat before you try coupling the supercontinuum into the fiber.
Insider tip
If you mount an achromat backward, spherical aberration will ruin your focal spot. Always face the more curved side toward the collimated beam.
Also heard as
- achromatic doublet
- doublet
Do not mix it up with
- Apochromat: An achromat corrects for two wavelengths, while an apochromat corrects for three and offers superior performance.