Changes in the spectral, coherence and polarization properties of stochastic electromagnetic beams on propagation.

摘要

In recent years, there has been a growing interest in the study of paraxial propagation of partially coherent, partially polarized, stochastic electromagnetic beams. Such beams are a generalization of scalar beams, which have been widely used in the study of changes in the spectral density and of the degree of coherence of fluctuating fields propagating through deterministic and random media. It is, however, important for many problems to consider the vector features of a light beam, for instance when studying polarization changes. By an appropriate generalization of the scalar theory of random fields to include vector effects, it becomes possible to study both coherence properties and polarization properties of stochastic electromagnetic beams.; The so-called electromagnetic Gaussian Schell-model (EGSM) beams are a generalization of the Gaussian shell-model beam, well-known in the scalar theory, to stochastic beams with orthogonal non-vanishing field components. In this thesis, we analyze the EGSM and derive necessary and sufficiency conditions which the parameters characterizing the beam satisfy, in order that the beam is physically realizable.; We then study spectral changes, changes in degree of coherence and changes in the degree of polarization of a partially coherent, partially polarized EGSM beam on propagation through a gradient-index (GRIN) fiber.; Using the model of EGSM beams we have attempted to elucidate the subtle relationship between coherence and polarization, using the Young's two-pinhole interferometer. We have also introduced the concept of statistical similarity for vector fields and used it to provide a physical interpretation of complete coherence of the field at two points and of complete polarization of the field at a single point.