diffraktionsgratings

A diffraction grating is an optical element with a periodic structure that diffracts incident light into several beams. The principal relation governing the angles of the diffracted light is d sin θ = m λ, where d is the groove spacing, θ is the angle relative to the normal, λ the wavelength, and m the diffraction order (an integer). For normally incident light, θ_m = arcsin(mλ/d).

Gratings are used to disperse light by wavelength. They can be transmission gratings or reflection gratings. Ruled gratings are produced by precise ruling of grooves, while holographic gratings are manufactured by interference in a photoresist layer. Blazed gratings have a sawtooth groove profile optimized for a specific wavelength to maximize efficiency in a chosen order.

Performance. The resolving power is R ≈ mN, with N the number of illuminated grooves. The efficiency depends on groove geometry, blaze angle, polarization, wavelength, and incident angle; typical peak efficiencies range from 60% to over 90% for optimized configurations. Higher diffraction orders enable shorter wavelengths but require order-sorting to separate overlapping spectra.

Applications. Diffraction gratings are central to spectrometers and monochromators in science and industry, used in optical telescopes, chemical analysis, and laser diagnostics. They enable high-resolution spectral measurements across UV, visible, and near-infrared regions. In astronomy, echelle gratings provide high dispersion.

Practical considerations. Grating spacing is commonly expressed as lines per millimeter (e.g., 600, 1200, 2400 l/mm). The choice affects spectral range and resolution. Surface quality, coating, and environmental conditions influence performance; calibration with known spectral lines is standard practice.