Polarisations

Polarisation (or polarization) is a property of waves and fields that describes the orientation and phase relationships of their oscillations. In electromagnetism, it most commonly refers to light, where the electric field vector oscillates in a particular direction as the wave propagates. A beam can be linearly, circularly, or elliptically polarized, and real-world light is often a mixture of polarization components, described by a degree of polarization ranging from 0 (unpolarized) to 1 (fully polarized).

Linear polarization occurs when the electric field oscillates in a fixed plane. Circular polarization has the electric field rotating with constant magnitude around the direction of travel, with right- or left-handed sense. Elliptical polarization generalizes these two cases. States can be characterized by Stokes parameters, which describe intensity and polarization orientation in a robust, experimentally accessible way, or by Jones vectors for fully polarized light. Malus’s law relates the transmitted intensity to the angle between the polarization direction and a polarizer for linearly polarized light.

Polarisation can be produced, altered, or analyzed with optical elements such as polarizers, waveplates, and birefringent materials, or by scattering. Detection methods include using polarizers, polarimeters, and interferometric techniques. Propagation through media, especially in fibers and crystals, can modify or degrade polarization; depolarization can arise from scattering, turbulence, or imperfections.

Applications are wide-ranging. Polarization is essential in liquid-crystal displays, sunglasses that reduce glare, and 3D cinema systems that separate polarization channels. In communications, polarization encoding can carry information. Polarization measurements also aid studies in astronomy, atmospheric science, and remote sensing, while in quantum information the polarization state of photons serves as a two-level quantum system for experiments on entanglement and information processing.