Polarization
Nonlinear Crystals and Nonlinear Optics

Natural light is only partially polarized. The individual light waves emitted are indeed linearly polarized, but there is no correlation between them in terms of direction, amplitude or phase. The emission is said to be incoherent. This means that the electric field vector $\overrightarrow{E}$ orthogonal to the light beam occupies all possible positions in a random fashion, projected onto a plane perpendicular to the beam. However, polarized sources do exist, including many lasers, and it is therefore important to define the usual polarization processes. In fact, the media known as polarizers allow only one...