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Monday 9th of december 2019, 1:30 pm, INSA Rennes

Gaëlle BRÉVALLE defends his PhD thesis

« Investigation of quantum dots VECSEL for the realization of a coherent dual wavelength laser »

VECSEL ; InAs/InP quantum dots ; dual-frequency laser ; saturated absorption spectroscopy ; SHB ; coupling


This PhD work focuses on several experimental studies, allowing to relate the performances of a dual-frequency laser to the structural and physical properties of quantum dots (QDs). These works aim to develop a new kind of VECSEL, integrating InAs/InP QDs emitting at 1.55 µm, in order to make tunable and robust (i.e. involving a weak coupling between the two modes) dual-frequency lasers. Firstly, a growth study of the QDs is realized. The control of the growth parameters ensures the control of the density and the inter-QDs distance, and thus of the electronic coupling. Following this study, the growth parameters are carefully selected to get high density QDs ; then the stack of the QDs planes forming the active medium is realized. The next study allowing the quantification of the photonic coupling by the homogeneous broadening and the electronic coupling is performed in quantum wells, quantum dashes and quantum dots, depending on the temperature and the carriers density. For this, saturated absorption spectroscopy, based on the Spectral Hole Burning (SHB) phenomenon, is used. The results obtained are linked to the last study that addresses the coupling between the two modes of the dual-frequency VECSEL by the measurement of the Lamb coupling constant. This measurement is performed in a quatum well based VECSEL first, to calibrate the experimental setup and to get the value for comparisons with QDs. Finally, preliminary results obtained in multimode operation of QDs based VECSEL are presented. They reveal to be very promising for the achievement of a dual-frequency operation.

(a) Temperature dependence SHB spectra for QWs and QDs. (b) Characteristics of our QDs VECSEL. (c) Evolution of the Lamb coupling constant in a dual-frequency QWs VECSEL, depending on the modes spectral difference.
Committee members
Sophie BOUCHOULE Director of research, C2N, Université Paris-Saclay Examinator
Guillaume CASSABOIS Professor, L2C, Université de Montpellier Examinator
Ghaya BAILI Research Engineer PhD., TRT, PalaiseauMember
Krassimir PANAJOTOV Professor, B-Phot, Vrije Universiteit Brussel Member
Cyril PARANTHOEN Assistant Professor, Institut Foton, INSA de Rennes PhD Manager
Mathieu PERRIN Assistant Professor, Institut Foton, INSA RennesPhD Manager
Mehdi ALOUINI Professor, Institut Foton, Univ Rennes 1 PhD Supervisor
Hervé FOLLIOT Professor, Institut Foton, INSA de RennesPhD Supervisor