what is grating element

A grating element is a term used in the context of diffraction gratings, which are optical elements that disperse light into its constituent wavelengths. A diffraction grating is an arrangement consisting of a large number of parallel slits of the same width and separated by equal opaque spaces. The combined width of a slit as well as a ruling in a plane diffraction grating is called the grating element. The spacing between the lines in a diffraction grating is of the order of the wavelength of visible light, and the number of lines in a plane transmission grating is of the order of 15000 to 20000 per inch. Diffraction gratings are often used in monochromators, spectrometers, lasers, wavelength division multiplexing devices, optical pulse compressing devices, and many other optical instruments.