Jury :

• Jean-François LAMPIN, Directeur de Recherche, Université de Lille (Directeur de thèse)
• Guillaume DUCOURNAU, Professeur, Polytech Lille (CoDirecteur de thèse)
• Jean-Pierre VILCOT, Directeur de Recherche, Université de Lille (Examinateur)
• Van Dijk FREDERIC, Ingénieur, III-V Lab (Examinateur)
• Anne-Laure BILLABERT, Maître de Conférences, Conservatoire national des arts et métiers (Rapporteur)
• Jean-François ROUX, Maître de Conférences, Université Savoie Mont Blanc (Rapporteur)

Summary:

Terahertz is a frequency range that is being studied more and more because of the special properties of this radiation. The low energy of photons makes them ideal for medical imaging, non-destructive testing in industry and studying the stars that surround us. The frequencies involved could also be used to increase telecommunications throughput, which is a major area of research at the moment. It is on this last aspect that this thesis is based, without restricting itself solely to this field. The increase in frequency required to increase throughput means that new sources and new antennas need to be found and optimised. The simulation of a unipolar transport photodiode or Uni-Travelling Carrier photodiode (UTC photodiode) structure is therefore carried out, enabling the optimisation of the photoresponse of these components to be validated. The second part concerns the design and demonstration of a new antenna concept, the aim of which is to be broadband and enable signals to be transmitted at several hundred GHz. In addition to telecommunications, the terahertz domain can be difficult to understand because its waves are invisible to the human eye, so it may be useful to develop cameras for viewing its beams. The final part of the thesis focuses on the specific case of detecting signals at 2.5 THz. The aim is to propose the architecture of an opto-thermo-mechanical MicroElectroMechanical System (MEMS) sensor, to manufacture it and to measure it so that it can be used, for example, in a camera at this particular frequency.

Abstract:

The terahertz domain is a frequency range, which interest keeps growing because of its properties. Because of the low energy of the photons, it becomes possible to use it for medical imaging, non destructive testing in the industry or even learn about the celestial objects around us. Its high frequencies also allow to increase the data bit rate, which is currently one of the main point of interest. This PhD thesis is mainly based on this aspect of the terahertz domain even though it is not completly restrained to it. The increase of telecommunication frequencies allows an increase in data rate but requires to find and optimize new sources and antennas. Therefore, simulations of a Uni-Travelling Carrier photodiode (UTC photodiode) structure were done in order to increase its photoresponse. A second part of this thesis is about the design, the fabrication and the characterization of a new kind of antenna which goal is to be broadband and to allow the transmission of signals which frequencies are over 300 GHz. In all its applications, the terahertz domain could be difficiult to grasp because its waves are invisible to the human eye. As a result, it would be useful to develop cameras to see those beams. The last part of the thesis is about the detection of signals at 2.5 THz where we propose two designs of a micro thermo-opto-mechanical system (MEMS). The systems are then fabricated and measured. The final goal would be to be able to use it as a single pixel in a terahertz camera at this frequency.