par Englebert, Nicolas 
Président du jury Kockaert, Pascal
Promoteur Gorza, Simon-Pierre
Co-Promoteur Leo, François
Publication Non publié, 2022-07-04
Président du jury Kockaert, Pascal
Promoteur Gorza, Simon-Pierre
Co-Promoteur Leo, François
Publication Non publié, 2022-07-04
Thèse de doctorat
| Résumé : | In this thesis, we study the formation of phase-locked, short-pulses in coherently driven, below-threshold laser cavities. Temporal cavity solitons formed in passive resonators are currently attracting a lot of attention because of their far-reaching connections to other nonlinear sciences and their wide-ranging applications. However, for practical reasons, their existence is limited to intrinsically low-loss resonators from which only a tiny fraction of the power can be extracted. We describe in this work how the addition of a carefully designed amplification section in a coherently driven resonator, pumped below the lasing threshold, allows exciting a new kind of optical pulse that we call active cavity soliton (ACS). We detail the theoretical model of this new scheme, highlighting how the ACS existence is affected by the gain saturation. We build such a resonator to confirm our predictions experimentally. Our measurements show that ACS possesses the robustness of passive resonator solitons while a significant fraction of the soliton’s energy can be extracted at each roundtrip, as the gain also partially compensates for these losses. The active scheme effectively removes the main constraint of having to work with low-loss resonators. In particular, we study two configurations where the high losses had so far prevented the study of the associated nonlinear phenomena: that of a cavity with a second-order nonlinear medium and that of one with a phase modulator. In the first configuration, we theoretically and experimentally show that ACSs can be driven with a laser at twice their carrier frequency. These parametrically driven cavity solitons (PDCSs) have no background and possess a phase multiplicity that we leverage to generate random numbers. Finally, in the second configuration, we show that the intracavity phase modulator introduces coupling be tween the frequency modes, generating a structure similar to that of a one-dimensional crystal: a synthetic dimension. We reveal its associated band structure and, by adding an effective force, demonstrate that ACSs exhibit a new kind of B LOCH oscillations. With a reduced model, we show how the driving, dissipation, dispersion, and nonlinearity influence these oscillations, originally arising in solid-state physics, in good agreement with the experimental results. |
