Terahertz waves correspond to the frequency band of 0.3-3 THz of the electromagnetic spectrum. This region of the spectrum has been considered as a gap since detecting and generating terahertz waves have always been a scientific and a technical challenge. The interesting properties of terahertz waves have been first applied in astronomy and spectroscopy. This has lead the scientific community to develop and invent new technical solutions for this frequency range.
Because of the interesting properties of terahert zwaves, applications have emerged in various domains such as medical imaging, security, safety, quality control and communication. However, the available solutions are bulky and difficult to integrate for portable applications.
Recently, different research groups have shown that standard silicon technology is a potential candidate to replace existing systems for terahertz generation and detection, enabling easy integration with on-chip readout and control electronics.
This PhD dissertation focuses on the design and analyses of room temperature terahertz direct detectors in different silicon technologies, their integration in a large camera system with on-chip readout and control electronics. The thesis addresses also the integration of control circuits for silicon based terahertz source arrays as well as imaging demonstrations.
The first step was to investigate single-pixel detectors in standard 65 nm CMOS bulk and 0.25 µm BiCMOS SiGe technologies. The detectors were antenna coupled and integrated in 3x5 pixel arrays. They made use of the non-linearity of standard devices for detecting the captured power by the integrated antennas. Novel detectors were investigated and led to state-of-the-art performance in terms of operation frequency and sensitivity in comparison with other research on silicon devices.
But, what arouses great interest in standard silicon implementations are the large scale integration possibilities. Therefore, as the second step of this thesis, a 1 k-pixel CMOS based terahertz camera was implemented in a collaborative teamwork during this thesis. It was considered as state-of-the-art device in terms of operation frequency and system integration. Other implementation concepts were investigated and analyzed in this thesis for scalable and adaptable readout circuits.
The implemented detector systems were designed for active illuminations. In fact, their sensitivity can not detect passive radiation from the environment. Therefore, artificial sources were needed. As the third step of this research work, a terahertz control circuit was implemented in a 0.13 µm BiCMOS SiGe technology for a 4x4 source array radiating at around 0.53THz .Control circuits for terahertz sources are a key feature to reduce power consumption and generate arbitrary patterns essential for terahertz active imaging.
As a final part of the thesis, terahertz imaging were demonstrated to show the capability of the implemented detectors, camera and sources. Scanned objects were shown at terahertz frequencies. Real-time terahertz imaging were demonstrated with the 1 k-pixel CMOS camera module as well as the evaluation of a monitoring application for a laboratory terahertz source.