What’s the diffraction grating?

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A diffraction grating is a material that breaks down white light into different colors. It is made of tempered glass with microscopic slits or lenses. It can be used for entertainment or scientific purposes, such as spectrometers. It creates a prism effect and can handle light differently depending on its type. Holographic and striped gratings are made from the same material. They are used in mass spectrometry and optical fibers. CDs and DVDs use holographic diffraction grating effects. Rifled grates have a special Blaze angle, and flame angles are used to focus the output.

A diffraction grating is a material or optical device usually designed to break down white light into the various colors of the visible spectrum. The material is a type of tempered glass like Pyrex with an aluminum coating and an epoxy layer in between populated by thousands of microscopic slits or lenses, also known as prisms. Depending on the quality of the diffraction grating material and the specific wavelengths of light it is intended to interact with, it can be used for low cost entertainment purposes such as specialized eyewear or in applications such as fiber optic data transmission and the spectrometers.

The grating essentially creates a prism effect over a large area that can have resolution down to the atomic scale. Light has different results when it passes through a diffraction grating depending on its type. Incoherent white light is split into all visible colors of the spectrum because each color of light is diffracted at a different angle as it exits the grating. Coherent laser light splits or diffracts on each side as it passes through the grating, producing repeating patterns of beams of decreasing intensity as they travel away to the left or right of where the laser entered the grating.

A striped diffraction grating has a higher degree of light handling efficiency than a holographic one, but both are built on the same principles and made from the same types of material. Holographic gratings are produced by a laser and photolithographic process. Lab-level gratings are made by a diamond bur that etches a reflective surface.

The reflection of multi-colored light that a compact disc (CD) or digital video disc (DVD) exhibits when exposed to light is an example of the holographic diffraction grating effect. This is caused by the fact that the tracks on the CD data storage disc are written at a fine enough level at about 1,600 nanometers wide, or less with a DVD, that they are capable of breaking visible light into the range about 600 nanometers. Holographic glasses with a diffraction grating are produced in a lower quality level, but produce the same basic visual effect.

More sophisticated diffraction gratings are used extensively in mass spectrometry to classify elements in compounds by exciting them as a gas with an electric discharge and passing the light produced through a diffraction grating. Rifled grates can also have a special Blaze angle relative to the slots. This means that the tiny prisms on the surface that break up the light have one end taller than the other, called a sawtooth profile.

Flame angles are used to focus the diffraction grating output onto a certain band region of the light spectrum. This is done to achieve maximum resolution in a particular band of light known as the Blaze wavelength. Other methods of targeting specific wavelengths of light include wavelength division multiplexing, used in optical fibers. By separating the different wavelengths, each can be used as an individual data stream and all can travel simultaneously along a fiber optic cable without interfering with each other.




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