Stokes parameters

Stokes parameters are a set of four values ​​, usually as S0 ... S3, or I, Q, U, and V is that of George Gabriel Stokes to describe the state of polarization of electromagnetic waves (generally light) was introduced in 1852. What is special about these values ​​is that they can be calculated by simple measurements of the light output after passing through various polarizers and so the polarization state can be determined quite easily.

The four Stokes parameters S0 ... S3 can be summarized to the so-called Stokes vector.

Analogously to the Jones vector, and the Jones matrix is treated, the effect on optical systems Stokes vectors in Mueller calculus by applying corresponding matrices ( Mueller matrix ).

Definition

The services are the measured power after passing through a horizontal (0 °), vertical ( 90 ° ), 45 ° and 135 ° oriented, ideal polarizer and the right-and left - circularly polarized component of the light.

Alternatively, they can be about the time-averaged amplitudes define the electric wave vectors in an orthogonal coordinate system, and their relative phase.

Usually, the Stokes parameters of the incident power are normalized by all four values ​​are divided by S0, one speaks in this connection of the normalized Stokes vector.

Defined in spherical coordinates

Another formulation is given in spherical coordinates:

Wherein the total intensity of the polarized component of the intensity, the tilt of the polarization ellipse and the ratio of the two main axes of the polarization ellipse.

Degree of polarization

The degree of polarization Π specifies how large is the parent portion of the wave. Defined by:

Respectively for only linearly polarized light:

For completely polarized light applies:

However, applies to unpolarized light:

Angle of maximum polarization

The angle of maximum polarization is defined by:

Where for, is otherwise. In other words, it means that you have to count 90 ° for added angles when less than.