A reflection grating is an optical element that achieves light reflection and dispersion by etching parallel lines on a highly reflective metal surface. It belongs to the category of multi-slit components and is mainly divided into two types: planar reflection gratings and concave reflection gratings. They are made by depositing an aluminum film on a glass blank and then etching parallel grooves with diamond. Common groove densities are 600 or 1200 grooves per millimeter, with the densest reaching 1800 grooves per millimeter. Aluminum is widely used due to its high reflectivity and ease of processing in the near-infrared to ultraviolet range. Planar reflection gratings, by optimizing the groove shape, can concentrate light energy to a specific order and are easy to replicate, gradually replacing prisms as the core component of spectrometers. Concave reflection gratings combine dispersion and focusing functions, mainly employing the Rowland device, Paschen device, and Eagle device based on the Rowland circle principle.
A grating is a multi-slit component. The generation of the grating spectrum is the result of the combined effects of multi-slit interference and single-slit diffraction. Multi-slit interference determines the position of spectral lines, while single-slit diffraction determines the intensity distribution of those lines. Gratings are divided into transmission gratings and reflection gratings, with reflection gratings being more commonly used. Reflection gratings can be further divided into planar reflection gratings (or blazed gratings) and concave reflection gratings (or simply concave gratings).