Blazed grating

It is optimized to achieve maximum grating efficiency in a given diffraction order.

, determining the magnitude of the wavelength splitting caused by the grating.

The grating lines possess a triangular, sawtooth-shaped cross section, forming a step structure.

The blaze angle is optimized to maximize efficiency for the wavelength of the used light.

Commonly blazed gratings are manufactured in the so-called Littrow configuration.

All other geometries yield anamorphic Littrow expansion or compression of the beam.

They are determined by the line spacing and can be calculated according to the in-plane version of the grating equation: where: For the Littrow configuration, this becomes

the blaze angle can be calculated for arbitrary combinations of diffraction order, wavelength and line spacing: Blazed gratings can also be realized as transmission gratings.

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 and PARAS (PRL Advanced Radial-velocity All-sky Search) spectrograph.

Diffraction at a blazed grating. The general case is shown with red rays; the Littrow configuration is shown with blue rays
Diffraction at a blazed grating. The general case is shown with red rays; the Littrow configuration is shown with blue rays