Thèse présentée par Isabelle Hantonne pour obtenir le grade de
Docteur en Physique de l’Université Sorbonne Paris Nord
Organic solid-state lasers (OSSLs) are promising coherent light sources for next-generation photonic technologies, offering broad spectral tunability, compatibility with flexible substrates, low manufacturing costs, and potential for large-area integration. However, major challenges remain, including continuous wave (CW) operation, electrical pumping, and the generation of controlled sub-nanosecond pulses under long-pulse or CW excitation. These limitations are related to non-radiative processes and intrinsic properties of organic semiconductors, such as exciton quenching, triplet state accumulation, and photodegradation.
This thesis addresses two key aspects of OSSL development: the reliable characterization of optical gain in organic materials, and the understanding and control of laser dynamics in transient regimes. First, the Variable Pump Intensity (VPI) method, based on Amplified Spontaneous Emission (ASE), is revisited; its limitations are characterized, and refined experimental protocols are proposed to allow a more robust evaluation of gain. The second part of the study focuses on organic lasers in transient regimes, studied using thin-film VCSEL and DFB structures. Ultrafast (picosecond) spontaneous dynamics, such as relaxation oscillations and spiking, are observed under diode pumping. Finally, passive Q-switching incorporating a saturable absorber – graphene – is explored for the controlled generation of sub-nanosecond pulses. This work contributes to positioning OSSLs as potential fast and integrable laser sources for optical communication. More generally, this thesis establishes the experimental foundations necessary for the development of the first organic solid-state laser generating sub-nanosecond pulses under diode pumping, thus opening new perspectives for ultrafast photonics.
Jury Member:
CASSETTE Elsa, ENS PARIS SACLAY, LUMIN, Rapporteur
ROMANELLI Marco, Université de Rennes, Institut FOTON , Rapporteur
LEBENTAL Mélanie, ENS PARIS SACLAY, C2N, Examinateur
BALEMBOIS François, IOGS, LCF, Examinateur
CHÉNAIS Sébastien, Université Sorbonne Paris Nord, LPL, Directeur de thèse
FORGET Sébastien, Université Sorbonne Paris Nord, LPL, Co-directeur de thèse
Keywords: Organic lasers, transient laser regime, relaxation oscillations, spiking, diode pumping, BSBCz, graphene
Soutenance : Le 25 Novembre 2025 à 14h30 Amphi Fermat