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Grating Diffraction Calculator

Calculate diffraction angles, angular dispersion, resolving power, and free spectral range for diffraction gratings using the grating equation.

A diffraction grating separates light into its component wavelengths by exploiting constructive interference at specific angles. The grating equation mλ = d(sin θᵢ + sin θₘ) relates groove spacing d, incidence angle θᵢ, diffraction order m, and diffraction angle θₘ. This calculator solves the grating equation for diffraction angles across a wavelength range, computes angular dispersion (dθ/dλ), theoretical resolving power (R = mN, where N is the number of illuminated grooves), and free spectral range (the wavelength interval before adjacent orders overlap). Useful for spectrometer design, monochromator alignment, and pulse compressor/stretcher layout in ultrafast laser systems.

Grating Parameters
Advanced Options
Primary Results
Groove Spacing (d)
1666.7 nm
Groove Spacing (d)
1.6667 μm
Diffraction Angle (β, m=1)
22.31°
Dispersion
Angular Dispersion
0.0372 °/nm
Angular Dispersion
0.6486 mrad/nm
Littrow & Free Spectral Range
Littrow Angle (θ_L, m=1)
10.94°
Free Spectral Range
632.8 nm
All Propagating Orders
Order (m)Angle β (°)
-2-49.41
-1-22.31
00
+122.31
+249.41
Abridged Optics — Grating Diffraction Calculator v1.0Calculations assume ideal grating behavior. Actual efficiency depends on groove profile, polarization, and coating.

All information, equations, and calculations have been compiled and verified to the best of our ability. For mission-critical applications, we recommend independent verification of all values. If you find an error, please let us know.