Sideband Injection Locking in Microresonator Frequency Combs

Frequency combs from continuous-wave-driven Kerr-nonlinear microresonators have evolved into a key photonic technology with applications from optical communication to precision spectroscopy. Essential to many of these applications is the control of the comb's defining parameters, i.e., carrier-envelope offset frequency and repetition rate. An elegant and all-optical approach to controlling both degrees of freedom is the suitable injection of a secondary continuous-wave laser into the resonator onto which one of the comb lines locks. Here, we study experimentally such sideband injection locking in microresonator soliton combs across a wide optical bandwidth and derive analytic scaling laws for the locking range and repetition rate control. As an application example, we demonstrate optical frequency division and repetition rate phase-noise reduction to three orders of magnitude below the noise of a free-running system. The presented results can guide the design of sideband injection-locked, parametrically generated frequency combs with opportunities for low-noise microwave generation, compact optical clocks with simplified locking schemes and more generally, all-optically stabilized frequency combs from Kerr-nonlinear resonators.Comment: 13 pages, 6 figure

Depletion-limited Kerr solitons in singly-resonant optical parametric oscillators

We analyze the impact of pump depletion in the generation of cavity solitons in a singly-resonant parametrical oscillator that includes a $\chi^{(3)}$ nonlinear section. We find an analytical expression that provides the soliton existence region using variational methods, study the efficiency of energy conversion, and compare it to a driven Kerr resonator modeled by the Lugiato-Lefever equation. At high walk-off, solitons in singly-resonant optical parametric oscillators are more efficient than those formed in a Kerr resonator driven through a linear coupler.Comment: 5 pages, 4 figure

An Experimental Investigation into the Evaluation of Explainability Methods for Computer Vision

EXplainable Artificial Intelligence (XAI) aims to help users to grasp the reasoning behind the predictions of an Artificial Intelligence (AI) system. Many XAI approaches have emerged in recent years. Consequently, the subfield related to the evaluation of XAI methods has gained considerable attention, with the aim of determining which methods provide the best explanation using various approaches and criteria. However, the literature lacks a comparison of the evaluation metrics themselves that could be used to evaluate XAI methods. This work aims to partially fill this gap by comparing 14 different metrics when applied to nine state-of-the-art XAI methods and three dummy methods (e.g., random saliency maps) used as references. Experimental results on image data show which of these metrics produce highly correlated results, indicating potential redundancy. We also demonstrate the significant impact of varying the baseline hyperparameter on the evaluation metric values. Finally, we use dummy methods to assess the reliability of metrics in terms of ranking, pointing out their limitations.EXplainable Artificial Intelligence (XAI) aims to help users to grasp the reasoning behind the predictions of an Artificial Intelligence (AI) system. Many XAI approaches have emerged in recent years. Consequently, the subfield related to the evaluation of XAI methods has gained considerable attention, with the aim of determining which methods provide the best explanation using various approaches and criteria. However, the literature lacks a comparison of the evaluation metrics themselves that could be used to evaluate XAI methods. This work aims to partially fill this gap by comparing 14 different metrics when applied to nine state-of-the-art XAI methods and three dummy methods (e.g., random saliency maps) used as references. Experimental results on image data show which of these metrics produce highly correlated results, indicating potential redundancy. We also demonstrate the significant impact of varying the baseline hyperparameter on the evaluation metric values. Finally, we use dummy methods to assess the reliability of metrics in terms of ranking, pointing out their limitations

Temporal solitons in coherently driven active cavities

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.Doctorat en Sciences de l'ingénieur et technologieinfo:eu-repo/semantics/nonPublishe

Positioning Map: a Visual Technique to Improve the Layout of Diagram Contextual Information

The presentation of information is a difficult activity. It requires to deal with model complexity, characterised among other things by the number of visual elements per diagram. In this position paper, we propose a positioning map constructed by combining the navigation and locator maps – two techniques resulting from the theoretical principles of effective communication. We believe that the positioning map is a better means than navigation and locator maps together to decompose models and to integrate their information cognitively. However, we still need to validate our proposal through empirical studies

Coupled active cavities for all-fiber Optical Frequency Comb Generation

info:eu-repo/semantics/publishe

Sideband Injection Locking in Microresonator Frequency Combs

Frequency combs from continuous-wave-driven Kerr-nonlinear microresonators have evolved into a key photonic technology with applications from optical communication to precision spectroscopy. Essential to many of these applications is the control of the comb’s defining parameters, i.e., carrier-envelope offset frequency and repetition rate. An elegant and all-optical approach to controlling both degrees of freedom is the suitable injection of a secondary continuous-wave laser into the resonator onto which one of the comb lines locks. Here, we study experimentally such sideband injection locking in microresonator soliton combs across a wide optical bandwidth and derive analytic scaling laws for the locking range and repetition rate control. As an application example, we demonstrate optical frequency division and repetition rate phase-noise reduction to three orders of magnitude below the noise of a free-running system. The presented results can guide the design of sideband injection-locked, parametrically generated frequency combs with opportunities for low-noise microwave generation, compact optical clocks with simplified locking schemes and more generally, all-optically stabilized frequency combs from Kerr-nonlinear resonators

Sideband injection locking in microresonator frequency combs

Frequency combs from continuous-wave-driven Kerr-nonlinear microresonators have evolved into a key photonic technology with applications from optical communication to precision spectroscopy. Essential to many of these applications is the control of the comb’s defining parameters, i.e., carrier-envelope offset frequency and repetition rate. An elegant and all-optical approach to controlling both degrees of freedom is the suitable injection of a secondary continuous-wave laser into the resonator onto which one of the comb lines locks. Here, we experimentally study such sideband injection locking in microresonator soliton combs across a wide optical bandwidth and derive analytic scaling laws for the locking range and repetition rate control. As an application example, we demonstrate optical frequency division and repetition rate phase-noise reduction to three orders of magnitude below the noise of a free-running system. The presented results can guide the design of sideband injection-locked, parametrically generated frequency combs with opportunities for low-noise microwave generation, compact optical clocks with simplified locking schemes, and, more generally, all-optically stabilized frequency combs from Kerr-nonlinear resonators