Holographic gratings are diffractive optical elements based on the principle of optical coherent superposition, utilizing the interference of two laser beams to form fringes. They can be fabricated on photosensitive materials using scanning interference field exposure technology. This technology involves coating a photosensitive material onto an optical glass substrate, followed by laser interference exposure and etching to create transmission or reflection gratings. The maximum groove density reaches 4300 lines/mm, and the maximum fabrication area is 1500mm × 420mm. Compared to traditional scribed gratings, they offer advantages such as no ghost lines, low stray light (10⁻⁴), and high resolution (reaching the theoretical value of 80%~100%). The diffraction efficiency can be increased to 95% using ion etching technology.
Holographic gratings are widely used in spectroscopic analysis instruments, astronomical telescopes, lasers, optical communications, and inertial confinement fusion, with typical applications including the "Xihe" satellite, AR-HUD systems, and AR glasses for specialized fields.
