polarisée

Polarisée, or polarized, describes a state in which a property has a preferred direction or orientation. In physics, polarization most commonly refers to the orientation of oscillations in electromagnetic waves, though the concept applies to other systems with directional order. For light, polarization can occur when photons are emitted by anisotropic sources, when light is reflected or scattered, or when it passes through a polarizing filter.

In optics, common polarization states are linear, circular and elliptical. Linear polarization means the electric field oscillates in a single plane; circular polarization arises when two orthogonal components are equal in amplitude and 90 degrees out of phase; elliptical polarization is the general case. Polarization states can be described by Stokes parameters and represented on the Poincaré sphere. Polarization is widely exploited in imaging, spectroscopy, astronomy, and communications.

Beyond optics, polarization describes how electric dipoles within a dielectric material align in response to an external electric field (dielectric polarization). Magnetic polarization, or magnetization, refers to the alignment of magnetic moments. Some materials exhibit spontaneous polarization, as in ferroelectrics, which can be reversed by an electric field.

Applications include polarizing filters used in photography and sunglasses, LCD screens that transmit light in selected polarization states, and 3D cinema that encodes two polarization channels. In science and engineering, polarization informs radar and remote sensing. In social science, polarization describes the increasing ideological distance between groups, which can affect discourse and policy outcomes.