Sinusoidal Holographic Grating
A sinusoidal grating is a diffraction grating that has a sinusoidal groove profile where the grooves are symmetrical and have no blaze direction. They are commonly produced using interference lithography which results in a smooth groove surface and eliminates the periodic errors found in ruled gratings.
Typically, a sinusoidal grating offers a wider spectral coverage compared to a blazed grating but has lower efficiency, however, under certain conditions where the groove spacing and wavelength ratio are close to unity, a sinusoidal grating can exhibit the same efficiency as a blazed grating. An example of this is an 1800g/mm sinusoidal grating, which has very high efficiency in the visible region.