Description du sujet de thèse

The PhD thesis topic is : Terahertz heterodyne camera using superconducting Hot Electrons Bolometer mixers
The objective of this thesis project is to build an ultra-sensitive THz receiver array for very high resolution spectroscopic imaging which requires heterodyne detection technique and in particular, the development of a multi-pixel mixer technology.
The Superconducting Hot Electron Bolometer (HEB) mixer has currently the best performances in terms of sensitivity for frequencies well beyond THz with noise temperatures close to the quantum limit. Our laboratory has a good expertise of THz HEB mixers. During the past R&T CNES actions and European RD programs, we have developed mixers with state-of-the-art sensitivities and new concepts of distributing and transmission of THz local oscillator (LO) signals. With a view to prepare ourselves to better meet the needs of future space observation missions, we plan to study new configurations of the mixer in order to allow its integration into a multi-pixel structure and realize an ultra-sensitive and compact heterodyne camera in the THz frequency range.
The realization of a heterodyne camera is more complex than a camera based on direct detection. A heterodyne receiver requires not only a good reception of the RF signal to be detected, but also that of the local oscillator. Effective extraction of the intermediate frequency signal is also crucial. Since the HEB mixer is sensitive to fluctuations of the bias circuit, the LO signal and the operating temperature, special attention must be paid to ensure good stability of the detection system.
In this research project, all the elements mentioned above will be examined. First, theoretical and experimental studies will be carried out in order to design and realize a very compact and built-in mixing module to allow 2D integration for the building of a matrix of THz mixers with high sensitivity without restrictions on the number or layout of pixels.
The second part of the thesis will be devoted to the integration of single-pixel modules to form a compact camera. Based on the work already carried out in the laboratory, the study on the structure distributing the LO signal to each pixel of the camera will also be performed. A prototype of the detection system is expected.

Contexte de travail

The LERMA is a joint research unit of the CNRS, the Observatoire de Paris, the Sorbonne Université and the Université Cergy Paris. The LERMA instrumentation group is a research and development team specialized in heterodyne detection between 100 GHz and 3 THz. With internationally recognized expertise in the design and manufacture of semiconductor and superconducting components and devices, the group's activities are oriented towards technological R&D and participation in instrument developments for space missions in several fields related to universe sciences and laboratory physics.
The thesis work will take place within the instrumentation group of LERMA. The doctoral student will enrol in the Doctoral School “Astronomie et Astrophysique d'Ile de France” (ED127) and follow the regular courses organized by the school. The thesis will be supervised by Yan Delorme (Lerma) and followed by a thesis committee that will accompany the student for the duration of the doctoral program. The doctoral student will receive a scholarship from the doctoral school.

Informations complémentaires

Holder of a Master's degree or an engineering degree, the candidate must have a good background in microwave electronics and in solid state physics (superconductor and semiconductor). He or she should be motivated, autonomous, and have the desire to approach and develop multiple skills. A good command of English is essential.