Super Finishing

Service Detail from Zygo Corporation


ZYGO's Super Finishing process produces extremely smooth surfaces over a wide power spectral density (PSD) band on materials such as fused silica, sapphire, YAG, etc. Our unique process (also known as Super Polishing) is capable of producing a surface roughness of < 1 Angstrom (< 0.1 nm), over spatial periods ranging from 10 nm to 1 mm.

This Super Finishing process can be accomplished on any size optic that we process, all the way up to meter-class optics. Super Finishing is most often performed on plano optics, like windows and mirrors, but can also be done on spherical or aspherical surfaces.

Why Super Finishing?

Super Finished surfaces are often required for applications where it is critical to reduce the scattering of light as it passes through the surface of an optic. This is especially important in applications using short wavelengths (such as X-ray optics), photolithography (especially EUV lithography), Fabry-Perot etalons, and instruments for high-performance telescopes, among many other applications.

Not All Super Finishes are the Same

Caution - when evaluating suppliers of precision optics, be sure to confirm what they define as "Super Finishing". The term "Super Finishing" (or "Super Polishing") does not have a standard industry-wide definition, so each supplier will have their own. Ask for the specifications of the surface they provide.

ZYGO has stringent specifications for our Super Finishedsurfaces (verified by ZYGO's world-class metrology). Our process is capable of producing a surface roughness of under 1 Angstrom (< 0.1 nm) over a wide range of spatial bands, i.e. from 10 nm to 1 mm. Other suppliers of Super Polished surfaces typically provide the desired roughness over a range of only 10 nm to 1 µm.

Surface Finish vs. Surface Form

Super Finishing and Super Polishing refer to the "roughness" of a surface, and is completely independent of surface form, which refers to the overall flatness or curvature of the surface. It is possible to have an optic with excellent surface form, but an inadequately smooth surface finish, and vice versa. The surface finish and surface form have very different specifications, so be sure to know what you need for each. ZYGO will be happy to help you determine these values based on your application.

Key Features

  • <1Å over a wide band of spatial periods (10 nm to 1 mm)
  • Can be performed on any size optic, up to meter-class
  • Materials: Fused Silica, Sapphire, YAG, etc.