Terahertz imaging from projections using a parallel plate waveguide aperture in transmission and reflection mode

Type Thesis

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Summary

Scope of study. Imaging resolution at terahertz frequencies is limited by the diffraction limit of the optics where the focus spot size is approximately on the order of a wavelength. We demonstrate a novel imaging technique that achieves sub-wavelength resolution at terahertz frequencies. A parallel plate terahertz waveguide is used as a near field imaging aperture in a transmission and reflection geometry. The image data is collected as projections of the target and are in the form of a radon transform. A reconstruction algorithm has to be used to extract the image from those projections. This type of reconstruction is similar to reconstruction techniques used in X-ray computed tomography (CT). Findings and conclusions. Using the near-field characteristics of the parallel plate waveguide, was possible to acquire images with sub-wavelength resolution. These images were then compared to images acquired using conventional diffraction limited optics and showed an increase in resolution in both transmission and reflection geometries. The highest achievable resolution was determined by the plate spacing of the parallel plate waveguide.