More on Diffraction Gratings

From the grating equation (ml=d sin q) it can be seen that the difraction angle depends on the spacing between the grating lines (d). A grating with a very closely spaced lines (d is very small) will diffract light at wide angles. It will have fewer diffracted orders, but its resolution will be greater than in a course grating. By this we mean that we can better distinguish between adjacent wavelengths (colors).

There are several different types of diffraction gratings. These include

Spectroscopy, or breaking light into its component wavelengths, is a common use of diffraction gratings. You might think that a prism would be used for this (sometimes they are) but the resolution obtained with a grating is much higher.

At a recent trade show visited by our SPIE student chapter, there were several types of spectrometers on display, as well as users of these same spectrometers. Manufacturers of optical filters, for example, need to measure the amount of each wavelength transmitted (or reflected) by their products.

The earliest diffraction gratings were made by room sized "ruling engines" that dragged a diamond stylus back in forth in parallel lines across a piece of glass. From this glass master grating, secondary gratings could be made using the glass master as a mold. The grating in your optics kit may have been made using holographic techniques. An example of a "common" reflection grating is a CD!