diffractors

A diffractor is any object or device that causes diffraction of waves, typically electromagnetic waves such as light, but also sound or matter waves. Diffraction refers to the bending and spreading of waves around obstacles and through apertures whose dimensions are comparable to the wavelength. Unlike a refractor, which alters a wave's direction mainly by changing the medium's refractive index, a diffractor modulates the phase and amplitude of a wave via its microstructure or geometry.

Common diffractors include diffractive optical elements (DOEs) such as zone plates, diffraction gratings, holographic patterns, and metasurfaces. These structures impose a spatially varying phase shift or transmission that distributes energy into specific diffraction orders. Diffractors can be designed to produce a single focusing or imaging function or to split and shape beams in complex ways.

Applications include beam shaping and splitting, spectral separation, imaging systems with compact focal lengths, and telescopes using diffractive lenses. In acoustics, diffractors manipulate sound fields; in electron or neutron optics, diffractive elements produce interference patterns. Programmable or tunable diffractors, such as spatial light modulators or active metasurfaces, enable dynamic control of diffraction patterns.

Design considerations include efficiency, wavelength dependence, and chromatic dispersion, which can limit performance across colors or frequencies. Higher diffraction orders may carry energy but with reduced efficiency, and manufacturing tolerances, polarization effects, and material losses can also affect outcomes. Diffractors range from simple gratings to advanced metasurfaces and remain central to controlling wave propagation in optical, acoustic, and quantum systems.