What is a diffraction grating?
A diffraction grating consists of a periodic groove structure upon which diffraction takes place. For this purpose glass plates with a plastic coating are usually used, embossed with a groove structure. A distinction is made between transmission and reflection gratings. In the case of a reflection grating, a thin, reflective metal coating is evaporated onto the groove structure.
In optics, for example, diffraction gratings are used in a monochromator to split polychromatic light into its individual wavelengths by means of interference and to direct the monochromatic light of one wavelength in a specific direction.
Compared to prisms, diffraction gratings have the advantage of much higher dispersion which, furthermore – unlike prisms – is not dependent on wavelength.
The most important specifications of diffraction gratings are their area, the number of lines or grooves per millimeter and the blaze wavelength. It determines the wavelength at which the diffraction grating achieves its highest efficiency. The more lines per millimeter a grating has, the more the light is split according to wavelength. In the case of a monochromator, the bandwidth of the monochromatic light is therefore smaller.
The image shows a diffraction grating illuminated with collimated white light.
Why do we need a diffraction grating?
In optics, for example, diffraction gratings are used in a monochromator to split polychromatic light into its individual wavelengths by means of interference and to direct the monochromatic light of one wavelength in a certain direction.
What can diffraction gratings consist of?
Mostly, glass plates with a plastic coating are used, embossed with the groove structure. A distinction is made between transmission and reflection gratings. In the case of a reflection grating, a thin, reflective metal layer is evaporated onto the groove structure.
What should you consider when choosing a grid?
Apart from size, the most important specifications of a diffraction grating are the number of lines or grooves per millimetre and the blaze wavelength. The blaze wavelength determines the wavelength at which the diffraction grating achieves its highest efficiency. The greater the number of lines per millimetre on the grating, the more the light is separated according to the wavelength. In the case of a monochromator, therefore, the bandwidth of the monochromatic light becomes smaller.
What are the advantage of diffraction gratings over prisms?
Compared to prisms, diffraction gratings have the advantage of a much higher dispersion, which, furthermore – unlike prisms – is not dependent on wavelength.
