Control of mid-infrared light dispersion and polarization with SiGe photonics / Contrôle de la dispersion et de la polarisation de la lumière infrarouge moyenne via la photonique SiGe

The mid-infrared is a key spectral range for spectroscopy and chemical sensing. Such applications could become accessible to a broad audience through photonic integration. In this context, this thesis explores the use of silicon-germanium (SiGe) photonics to control two properties of quantum cascade lasers (QCLs): dispersion and polarization. First, dispersion control using variable-period Bragg gratings combined with a multimode interferometer enabled the generation of 1.39 ps ultrashort pulses around 8 µm from a QCL frequency comb. Second, a polarization rotator consisting of a mode-evolution waveguide and an asymmetric directional coupler was developed, demonstrating a conversion rate exceeding 88% between 7.5 and 8.9 µm. These achievements constitute essential building blocks for the development of fully integrated spectroscopic systems.

Jury members : 

• • Joël Charrier, Université de Rennes
  • Kamel Merghem, Telecom SudParis
  • Carlo Sirtori, Ecole Normale Supérieure
  • Jérôme Faist, ETH-Zürich
  • Bart Kuyken, Ghent University