Useful Wavelength Range of Diffraction Gratings

The laws governing diffracted efficiency are quite complicated, but a very rough rule of thumb can be used to estimate the useful range of wavelengths available on either side of the blaze (peak) wavelength B for triangular-groove gratings.

Coarse Pitch Diffraction Gratings

For coarse gratings (for which d ≥ 2λ), the efficiency in the first diffraction order is roughly half its maximum (which is at λB) at 2λB/3 and 3λB/2. Curves of similar shape are obtained in the second and third orders, but the efficiencies are typically 20% less everywhere, as compared with the first order.

Fine Pitch Diffraction Gratings

Grating of fine pitch (d ≈ λ) have a somewhat lower peak efficiency than do coarse gratings, though the useful wavelength range is greater.

Diffraction Gratings Handbook Cover

For footnotes and additional insights into diffraction grating topics like this one, download our free MKS Diffraction Gratings Handbook (8th Edition)

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