The polarization state is one of the fundamental characteristics that is required to study light. There are three states of polarization that are used to describe light:
If the polarization of all the electromagnetic waves in a light beam can be made so that each of the electric or magnetic field vector to have the same orientation, then the light beam is said to be polarized. Because of this, there is then a unique plane which contains all the directions of the electric or magnetic field along with the light rays. This type of polarization is referred to as plane polarization or linear polarization.
The second polarization state is referred to as circular polarization. Circular polarization can be described as the vectors of the electric field is rotated at a point in space in the direction that is perpendicular to the plane of propagation, instead of fixed orientation oscillation. The electric field vector magnitude also remains unchanged.
Circular polarization can be further classified according to the rotation. Looking at the oncoming light wave, if the electric field vector of the light appears to be rotated in a clockwise direction, then the wave is referred to as right-circularly polarized. On the other hand, if the light vector appears to rotate in a counterclockwise direction, then the wave is said to be left-circularly polarized.
The third state of polrization is called elliptical polariztion. Elliptically polarized light consists of two light waves that are linearly polarized and having unequal amplitudes but has the same frequency. This results in a light wave with electric vectors that both rotates and changes its magnitude. An elliptical shape can be traced out by the tip of the electric field vector, and therefore it is referred to as elliptical polarization.
It is also worthy to mention that circular polarization is a special case of elliptical polarization.