BORIS Theses

BORIS Theses
Bern Open Repository and Information System

Coherent lensless imaging techniques using terahertz radiation

Valzania, Lorenzo (2019). Coherent lensless imaging techniques using terahertz radiation. (Thesis). Universität Bern, Bern

19valzania_l.pdf - Thesis
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Terahertz (THz) radiation denotes the portion of the electromagnetic spectrum lying between the infrared and microwave bands, corresponding to frequencies in the range 0.1-10 THz. The most intriguing feature of using THz waves is their ability to penetrate several non-conducting and optically opaque materials, such as plastics, textiles, paper, and some building materials as well as intrinsic semiconductors. While this property is also shared by microwaves, THz radiation provides a better spatial resolution thanks to the shorter wavelength, thereby imaging hidden objects with sub-millimeter resolution. The non-ionizing nature of THz radiation when it interacts with living tissues also makes THz imaging techniques promising for biomedical and biological applications. In this thesis, I focus on the development and implementation of THz imaging techniques. All the techniques presented here belong to the realm of coherent lensless imaging, aiming at reconstructing the amplitude and phase of the wavefront diffracted by an unknown object, illuminated with coherent radiation, based on measurements of the intensity of their diffraction pattern recorded with a camera. The fact that the imaging process is carried out fully computationally and without the need of lenses has a crucial impact on the experimental setup, which is therefore compact and can be better tailored to real-life applications. In particular, I am going to discuss both theoretical and experimental aspects of synthetic aperture THz off-axis digital holography, the first experimental demonstration of THz ptychography and how to image objects hidden behind weakly and strongly diffracting barriers. A potential biomedical application for such THz imaging techniques will also be suggested.

Item Type: Thesis
Dissertation Type: Single
Date of Defense: 6 June 2019
Subjects: 600 Technology > 620 Engineering
Institute / Center: 08 Faculty of Science > Institute of Applied Physics
Depositing User: Hammer Igor
Date Deposited: 02 Sep 2019 15:13
Last Modified: 02 Sep 2019 15:13

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