Types of polarized light

Light is an electromagnetic wave, and the direction of vibration of the electric field is perpendicular to the direction of propagation. The electric field vibration direction of ordinary light is random, such as sunlight, halogen light, etc. Then, if the electric field changes with time in a vertical cross-section of the direction of light propagation, such light is called polarized light. In optical design, engineers often pay more attention to the wavelength and intensity of light, but ignore its polarization index, in fact, polarization is an important characteristic of light, using the polarization of light can achieve a variety of applications.

Linearly polarized light

The electric field direction of light is limited along the direction of propagation to a plane (the y-z plane) whose magnitude varies with phase, and on the cross section perpendicular to the direction of propagation (the x-y plane), the trajectory of the endpoints of the light vector is a straight line.

Circularly polarized light

The electric field of light consists of two linear components that are perpendicular to each other and have equal amplitudes but a phase difference of 90°. During the propagation of circularly polarized light, the size of its vector is unchanged, the direction rule changes, in the cross section perpendicular to the direction of propagation (x-y plane), the trajectory of the end point of the light vector is a circle, according to the direction of rotation, divided into left-handed or right-handed circularly polarized light.

Elliptically polarized light

The electric field of light consists of two linear components with different amplitudes and/or that are not 90° in phase. The magnitude and direction of the light vector of elliptically polarized light change regularly during propagation. On the cross section perpendicular to the propagation direction (x-y plane), the trajectory of the end point of the light vector is an ellipse. This is the most general description of polarized light, and circular and linearly polarized light can be viewed as the two extremes of elliptically polarized light.