Holographic Grating

A holographic diffraction grating is produced using a photolithographic process that records a holographic interference pattern onto a photosensitive surface. Two intersecting laser beams create equally spaced interference fringes, which are projected onto a photoresist-coated substrate. The photoresist is then developed, dissolving in proportion to the light intensity, to form a precisely defined sinusoidal groove pattern. Finally, the grating surface is coated with a reflective layer to enhance performance.

Because holographic gratings are generated from an optical interference pattern rather than mechanical ruling, they are free from periodic errors and ruling imperfections. This results in extremely low stray light and no ghosting effects, providing superior spectral purity compared to ruled gratings (See Ruled Grating vs Holographic Grating ffor a detailed comparison).

Holographic gratings can also be blazed to optimize efficiency over a specific wavelength range, combining the low stray light performance of holographic fabrication with the high efficiency of a blazed profile.