Data for calculation

Light of wavelength λ incident at an angle i will be diffracted at angles i' given by:
                          sin i'=Gnλ - sin i
where G = groove density (lines/mm) and n is the order of diffraction (any integer). Blazed gratings have facets inclined at an angle b to the surface to concentrate light into the first order (n = +1). When the grating used in the Littrow condition (retroreflection, i = i') peak efficiency will be near the blaze wavelength shown (=(2/G)sin b).