Pulsed three dimensional THz imaging

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Tezin Türü: Yüksek Lisans

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Fen Edebiyat Fakültesi, Fizik Bölümü, Türkiye

Tezin Onay Tarihi: 2016

Öğrenci: BURCU KARAGÖZ

Danışman: HAKAN ALTAN

Özet:

In this thesis, a Terahertz Pulsed Imaging (TPI) system based on Terahertz Time Domain Spectroscopy (THz-TDS) was constructed to non-destructively evaluate and image samples. By scanning samples in the time domain, three dimensional (3D) views of sample geometries were generated. In order to image samples in 3D, a THz-TDS system based on reflection mode which permits the scanning of samples across THz beam was constructed. Thus, third axis which characterizes the depth profile of samples was obtained. THz pulse was focused on samples with an angle of incidence of 34° to a measured spot diameter of 3 mm. In the system, InGaAs based photoconductive antennas (PCAs) were used for THz generation and detection and a bandwidth up to 1 THz was obtained. Terahertz images of two different types of samples were presented to examine the constructed THz imaging system. The first sample was composed of acetate layers and letters cut from aluminium foil which were placed at various cross sections in depth. The second sample type was tooth slices of thickness ~ 1 mm sectioned mesiodistally in parallel. These tooth samples were prepared by the Faculty of Dentistry of Ankara University in Ankara, Turkey. By using this system, 3D images of the layered sample could be extracted by performing a time domain analysis although THz images were obtained from raw THz data. It has also been shown that THz imaging can be used to detect and monitor dental caries.