Degenerate four-wave interference and perfect blaze

The recently calculated high diffraction efficiencies for TE- and TM-polarizatized light (perfect blaze) for echelette gratings are explained by degenerate four-wave interference, which is formed as a double periodical pattern in the cross section of the grating plane. The blazed grating profile should match this interference pattern for a single reference light wavelength. The recently published data are the special case of a general design. The prognoses of the model are connected with large grating constants in comparison with the light wavelength, where short grating constants need comparison with numerical methods.