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Blazed grating

Blazed grating

A blazed grating combines diffraction with reflection in order to put most of the light into one diffracted order. A grating may, therefore, be described as "blazed at 250 nm" or "blazed at 1 micron" etc. by appropriate selection of groove geometry. A blazed grating can be one in which the grooves of the diffraction grating are controlled to form right triangles with a "blaze angle, q". Blazed grating groove profiles are calculated for the Littrow condition where the incident and diffracted rays are in auto collimation. The input and output rays, therefore, propagate along the same axis. In this case at the "blaze" wavelength l :

Grating equation

In the Littrow condition incident and refracted angle are equal to the Blaze angle. We therefore find fot the blaze wavelength: Blaze wavelength

 

First published on the web: 19.11.2007

Authors: Aranka Derzsi and Giovanni Lotito. The text is based on a lecture given by Thomas Nelis at the first Gladnet training course in Antwerp Sept. 2007