Refleksionsgitter

Refleksionsgitter, or reflection grating, is a diffraction element used in optical spectroscopy to disperse light by reflection. It consists of a reflective substrate bearing a periodic groove pattern. When illuminated, the grooves cause interference of the reflected waves, producing constructive interference at specific angles and thereby spreading light into a spectrum.

The optical behavior is described by the grating equation mλ = d (sin α + sin β), where d is the groove spacing, α is the angle of incidence, β is the angle of diffraction, and m is the diffraction order. For a reflection grating, both the incident and diffracted beams lie on the same side of the grating normal, with the grating typically mounted to adjust α and obtain the desired β.

Groove density (grooves per millimeter) and the groove profile determine performance. A blaze angle shapes the groove facets to maximize efficiency in a chosen order and wavelength range, directing most energy into a particular m. Two main types exist: ruled gratings, created by mechanical ruling of grooves, and holographic gratings, produced by interference patterns. Echelle gratings are a subset with very high blaze angles for high-resolution work, often used with cross-dispersion to separate spectral orders.

Compared with transmission gratings, reflection gratings handle reflective illumination and are well suited to ultraviolet and infrared regions with appropriate coatings. Efficiency depends on groove geometry, polarization, and spectral order, and order-sorting may be required to prevent overlap.

Applications span astronomical spectrometry, laboratory analysis, and industrial sensing across UV to near-infrared wavelengths. Materials and coatings (such as aluminum, silver, or specialized dielectric stacks) are chosen to optimize reflectivity for the target wavelength range.