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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Analysis of three-dimensional field distributions for focussed unapodized/apodized annular beams

Bhabu, Shaleen J. 13 February 2009 (has links)
The study of focal shift in focused beams using unapodized apertures has been well documented. However, not much work has been done on apodized apertures. In this thesis we use a Fourier-Optic approach to analyze the field distribution of a focused beam around the region of geometrical focus. The analytical formulation developed is general in nature as it is valid for any arbitrary aperture functions. This is then applied to some specific cases. Two cases of interest that are considered are the unapodized and the Gaussian apodized annular apertures. In order to study the intensity distributions around the geometrical focus, simulation results are presented using closed form analytical expressions and approximate integral forms. Specific emphasis is placed on the focal shift in the two apertures and on the effect of changing various parameters. A prognosis for future work using a-Modulation on Gaussian apodized annular apertures is also presented. / Master of Science

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