Photonique intégrée sur verre pour la génération de fréquences Térahertz

Sujet de thèse 2023
Photonique intégrée sur verre pour la génération de fréquences Térahertz

The thesis will focus on the development of co-integrated Glass DFB Lasers for THz generation and  the demonstration to high speed communications. Several advanced applications, such as next wireless  communication system (6G and beyond), spectroscopes and radars require high purity radio frequency  signals. These lasts are more and more difficult to generate as the signal frequency increases using  conventional electrical techniques. Solutions based on heterodyning of optical sources have  demonstrated to be the preferred way to produce frequencies higher than 100GHz (aka THz  frequencies).
We already demonstrated the potential of the ion exchanges platform for the generation of 300GHz communication signals, y integrating several lasers in a single glass chip. The intrinsic coherence of  those lasers, several orders of magnitude better than those based on other integrated technologies allow implementing advanced modulation formats such as QAM and OFDM to further improve the  transmission capabilities of THz communication systems.

The objective of this PhD is to enhance the performances our integrated glass chips to reach frequency  up to 600GHz. Different solutions have already been identified, like integrating distinct Bragg gratings in a single glass chip for example. The laser stability will also be improved through the insertion of
phase shifts in laser cavities.
Another objective is to integrate specific technologies to enhance the module: we will associate two  different chips in a single module for specific functions. One module will be dedicated to the laser  sources, and another module will consist of advanced Lithium Niobate modulators dedicated to optical  coherent communications. The multi-chip module will be integrated in a compact package, interfaced  with optical fibres and electrical DC and RF ports.
In order to qualify the modules and demonstrate their potential for high demanding applications such  as telecommunication, advanced characterization will be implemented. As an example, both spectral  and time domain characterisation will be analysed to study the laser frequency noise dynamic and  noise transfer to the THz signal during the heterodyning process. Detailed studies based on frequency  Allan variance will be used to qualify and determine the different contributions to laser linewidth.
Finally, the chips will be inserted in communication links using advanced modulation formats to  demonstrate the capabilities of the ion exchange platform for THz communications.

The PhD work will benefit from worldwide recognized know-how and facilities of the IMEP-LAHC  laboratory, including clean rooms access, and advanced characterizations set-ups. Some aspects of the  work will benefit from existing collaborations, for modulator chip, for advanced THz characterizations
and system demonstrations.

As the applicant will work in an interactive team and will be in direct contact with industrial and  academic partners, we are looking for someone willing to work in a collaborative environment. The  work requires experimental fabrication, characterization and analysis, but also strong theoretical  knowledge to understand the origin of the system perturbations and their impacts on the final  application. Consequently, we are looking for candidates having susceptibility for experimental work,  and strong will to develop their theoretical backgrounds in the following fields:
Laser Physics, High speed optical systems, Noise analysis.

Starting date: Oct. 2023
For more details, please contact:
Julien POËTTE
Lionel BASTARD
Jean-Emmanuel BROQUIN

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