Zwiggelaar, Reyer; (1993) Coherence and polarisation phenomena in optical systems and fibres for signal processing. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

For the (pre-)processing of electro-magnetic fields the coherence and polarisation aspects are important entities. Both coherence and polarisation are used in their broadest sense, in which case one can talk about the general correlation aspects of such fields. In this thesis two special aspects of the coherence and polarisation of electromagnetic fields are discussed after a more general treatment of the correlations in those fields is given. The first specialised subject of this thesis deals with the changes in both the polarisation and the degree of polarisation upon propagation in optical fibres. Theoretical results are derived, using a single Mueller matrix, to describe the polarisation along the optical fibre taking into account both the coupling and difference between the orthogonal polarisations present in the fibre. This newly developed theory is compared with other recent theoretical approaches (e.g. the mode coupling centre approach) and with measurements involving a range of different physical situations (e.g. difference in input degree of polarisation, spectral linewidth and kind of fibre). Links between the temporal and spatial coherence of electro-magnetic fields are discussed as the other specialised subject of this thesis. The emphasis is on spectral changes as a function of the spatial coherence of the field. These changes are now known as the "Wolf-effect" after one of the founders of this field of research. One possible way to describe these spectral changes is to use the well established cross-spectral density approach. However, it is shown that a quasi-optical method gives similar results. Theoretical results are compared with a number of experiments, including free space propagation. Young's experiment and propagation in inhomogeneous media. For both of the specialised subjects mentioned above possible applications and future research are discussed at various places in this thesis.

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