Diffraction Grating

衍射光栅

When there is a need to separate light of different wavelengths with high resolution, then a diffraction grating is most often the tool of choice. This "super prism" aspect of the diffraction grating leads to application for measuring atomic spectra in both laboratory instruments and telescopes. A large number of parallel, closely spaced slits constitutes a diffraction grating. The condition for maximum intensity is the same as that for the double slit or multiple slits, but with a large number of slits the intensity maximum is very sharp and narrow, providing the high resolution for spectroscopic applications. The peak intensities are also much higher for the grating than for the double slit.

当需要以高分辨率分离不同波长的光时，衍射光栅通常是首选工具。这种‘超级棱镜’特性使得衍射光栅在实验室仪器和望远镜中被用于测量原子光谱。大量平行且间距紧密的狭缝构成了衍射光栅。强度最大值的条件与双缝或多缝相同，但由于狭缝数量多，强度最大值非常尖锐且狭窄，为光谱学应用提供了高分辨率。与双缝相比，光栅的峰值强度也更高。

When light of a single wavelength , like the 632.8nm red light from a helium-neon laser at left, strikes a diffraction grating it is diffracted to each side in multiple orders. Orders 1 and 2 are shown to each side of the direct beam. Different wavelengths are diffracted at different angles, according to the grating relationship.

当单色光，例如左侧氦氖激光器发出的632.8纳米红色光，照射到衍射光栅上时，它会被衍射到两侧的不同级次中。1级和2级的衍射光分别显示在直接光束的两侧。不同波长的光会被衍射到不同的角度，这遵循光栅关系。

Diffraction Grating

衍射光栅

A diffraction grating is the tool of choice for separating the colors in incident light.

衍射光栅是分离入射光中不同颜色的首选工具。

This illustration is qualitative and intended mainly to show the clear separation of the wavelengths of light. There are multiple orders of the peaks associated with the interference of light through the multiple slits. The intensities of these peaks are affected by the diffraction envelope which is determined by the width of the single slits making up the grating. The overall grating intensity is given by the product of the intensity expressions for interference and diffraction. The relative widths of the interference and diffraction patterns depends upon the slit separation and the width of the individual slits, so the pattern will vary based upon those values.

The condition for maximum intensity is the same as that for a double slit. However, angular separation of the maxima is generally much greater because the slit spacing is so small for a diffraction grating.

衍射光栅的光强最大值条件与双缝相同。然而，由于衍射光栅的缝间距非常小，最大值的角分离通常要大得多。

The diffraction grating is an immensely useful tool for the separation of the spectral lines associated with atomic transitions. It acts as a "super prism", separating the different colors of light much more than the dispersion effect in a prism. The illustration shows the hydrogen spectrum. The hydrogen gas in a thin glass tube is excited by an electrical discharge and the spectrum can be viewed through the grating.

衍射光栅是分离与原子跃迁相关的谱线极其有用的工具。它作为一种‘超级棱镜’，能够比棱镜的色散效应更有效地将不同颜色的光分开。图中显示了氢谱。氢气在细玻璃管中被电弧激发，谱线可通过光栅观察。

The tracks of a compact disc act as a diffraction grating, producing a separation of the colors of white light. The nominal track separation on a CD is 1.6 micrometers, corresponding to about 625 tracks per millimeter. This is in the range of ordinary laboratory diffraction gratings. For red light of wavelength 600 nm, this would give a first order diffraction maximum at about 22° .

紧凑盘上的轨道可以视为衍射光栅，使白光的色散得以实现。CD上的名义轨道间距为1.6微米，对应约每毫米625条轨道。这处于普通实验室衍射光栅的范围内。对于波长为600纳米的红光，这将导致一级衍射极大值出现在约22°的位置。

这张图是定性的，主要目的是展示光的波长分离。与通过多个狭缝的光的干涉有关的峰有多重次序。这些峰的强度受到衍射包络的影响，而该包络由组成光栅的单个狭缝的宽度决定。光栅的整体强度由干涉和衍射的强度表达式乘积给出。干涉和衍射图案的相对宽度取决于狭缝间距和单个狭缝的宽度，因此图案会根据这些值而变化。