Polarization (electrostatics)
In electrostatics, the polarization is the vector field that results from permanent or induced electric dipole moments in a dielectric material. The polarization vector P is defined as the dipole moment per unit volume.
In a homogeneous linear and isotropic dielectric medium, the polarization is aligned with and proportional to the electric field E:
- P = ε0χE ,
where ε0 is the permittivity of free space, and χ is the electric susceptibility of the medium.
If the polarization P is not proportional to the electric field E, the medium is termed nonlinear and is described by the field of nonlinear optics. If the direction of P is not aligned with E, as in many crystals, the medium is anisotropic and is described by crystal optics.
