Studies on Partially Coherent Fields and Coherence Measurement Methods PDF Download

Author: Seongkeun Cho
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ISBN:
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Languages : en
Pages : 129

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Book Description
"The concept of coherence in optics means how closely an optical field oscillates in unison at the same position in different time (temporal coherence) or at different positions at the same time (spatial coherence). Since all optical fields oscillate very rapidly with random fluctuations, coherence theory has been developed to describe the state of coherence of those optical fields through the usage of time-averaged correlation functions. This thesis reviews and applies coherence theory for an accurate and improved modeling in field-propagation and coherence measurement for partially coherent fields. The first half of this thesis discusses the study of phase-space distributions and phase-space tomography. Phase-space distributions such as the Wigner and the ambiguity functions can be used as simple mathematical tools for describing the propagation of an optical field for any state of coherence as those functions incorporate wave effects with the simplicity of ray optics. However, the Wigner and the ambiguity functions require a paraxial condition for the field description. To overcome this limitation, the nonparaxial extensions of the Wigner function have been studied and applied for nonparaxial fields. In this thesis, a simple series expression for calculating a nonparaxial generalization of the Wigner function from the standard Wigner function is developed in both two- and three-dimensional free space. A nonparaxial generalization of the ambiguity function that retains properties analogous to the standard ambiguity function is also proposed in both two and three dimensions. This generalization extends phase-space tomography to the nonparaxial regime. The second half of this thesis proposes a new method of coherence measurement based on diffraction. By measuring the radiant intensity of a field with and without a binary transparent phase mask, one can estimate the coherence of a field at all pairs of the points centered at the mask's edge. This method is proposed in both two and three dimensions, and simple measures of the levels of error of this scheme are also derived. The numerical and experimental results validate the proposed method. This proposed scheme can also be extended to phase masks that are not transparent"--Page vi-vii.