2. Diffraction gratings

Two different types of component have been used for light dispersion: the prism and the diffraction grating. Most systems currently on the market use the grating, because of its better dispersion characteristics. A diffraction grating consists of a series of periodic, parallel lines on a flat or concave surface. These lines impose a periodic variation, in amplitude and phase, on an incident wave. The first grating was designed by Fraunhofer, and the first concave grating was engraved by Rowland in 1890. Although gratings can work by transmission, only reflection gratings are currently used.

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