StokesFormalismus

The Stokes formalism is a framework in polarization optics that describes the polarization state of light using four real numbers known as the Stokes parameters: S0, S1, S2, and S3. The Stokes vector S = [S0, S1, S2, S3]^T provides a compact representation that is well suited for both fully and partially polarized light.

S0 represents the total intensity of the light beam. The parameters S1, S2, and S3 quantify the state of polarization: S1 is the difference in intensity between horizontal and vertical linear polarization, S2 is the difference between linear polarizations at +45 degrees and −45 degrees, and S3 is the difference between right-handed and left-handed circular polarization. Together they encode all polarization information in a way that remains meaningful under common optical transformations.

Geometrically, the normalized three-vector (S1/S0, S2/S0, S3/S0) corresponds to a point on the Poincaré sphere for completely polarized light, with partially polarized light lying inside the sphere. The Stokes formalism thus provides a convenient bridge between classical polarization analysis and more abstract representations such as the Jones calculus (for fully polarized light) and the coherency matrix (for statistical mixtures).

The formalism extends to the Mueller calculus, where optical elements are described by 4×4 Mueller matrices that transform Stokes vectors. This makes it possible to model the effect of complex optical systems, including depolarization, on arbitrary polarization states.

Applications of the Stokes formalism span polarimetry, astronomy, remote sensing, ellipsometry, and optical communications, where robust, measurement-friendly descriptions of polarization are essential.