Year: 2015
Type: dissertation
Abstract: This thesis investigates partial polarization and coherence of stationary and nonstationary fields within the context of classical electromagnetic coherence theory.Temporal fluctuations of the instantaneous polarization state are considered in non-beamlike stationary random fields by means of a polarization correlation function.The fluctuations of fields obeying Gaussian statistics are found to be explicitly connected to partial coherence and partial polarization.Complete electromagnetic coherence is studied in both time and frequency domains in terms of statistical similarity, and it is pointed out that statistical similarity of two fully polarized fields is equivalent to them being completely coherent.In contrast to scalar fields, strict cross-spectral purity, together with complete spectral coherence, is determined to be a sufficient, but not necessary, condition for complete coherence in the space-time domain.A systematic theory of partial polarization and partial coherence in nonstationary electromagnetic fields is introduced and applied to the analysis of a temporal imaging system.The results show that such a system may be used to generate a wide variety of polarization effects.The coherent-mode decomposition (CMD) for nonstationary electromagnetic fields is also put forward, and the space-time domain and space-frequency domain mode structures are shown to be directly connected via a Fourier transform relation.Coherent modes of the electric and magnetic components of a stationary electromagnetic field are studied in a spherical volume, and it is shown that the electric and magnetic mode structures are, in general, different from each other.Propagation of coherent modes is studied in the paraxial approximation and for general fields.Paraxial propagation is found to preserve the mode structure, while in the nonparaxial case this is achieved only for free fields.
Author: Timo Voipio
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: KAUTE-Säätiö, Emil Aaltosen Säätiö
OpenAlex ID: W3185592435