echelle grating

Echelle gratings are, like other types of diffraction grating, used in spectrometers and similar instruments.

In echelle gratings, however, this behaviour is deliberately used and the blaze is optimized for multiple overlapping higher orders.

Echelle gratings are mostly manufactured with larger line spacing but are optimized for higher diffraction orders.

Echelle gratings are useful in planet-finding astronomy, and are used on the successful HARPS spectrograph.

In the optical regime, in which the use of gratings is most common, this corresponds to wavelengths between 100 nm and 10 m. In that case, the groove density can vary from a few tens of grooves per millimeter, as in echelle gratings, to a few thousands of grooves per millimeter.