Blazing of Ruled Transmission Gratings

Because they have no metallic overcoating, triangular-groove transmission gratings display far simpler efficiency characteristics than do their ruled counterparts. In particular, transmission gratings have efficiency curves almost completely free of polarization effects.

The peak wavelength generally occurs when the direction of refraction of the incident beam through a groove (thought of as a small prism) equals the direction dictated by the grating equation. [This is in direct analogy with the model of reflection grating blazing in that the grooves are thought of as tiny mirrors; see Diffraction Grating Efficiency.] Due to the index of refraction of the grating, though, the groove angle exceeds the blaze angle for a transmission grating.

Diffraction Gratings Handbook Cover

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