Yifan Sun

We demonstrate temporal pattern formation in a coherently driven fiber ring cavity whose effective finesse is continuously reconfigured using distributed Raman amplification. We achieve an effective finesse of up to Feff≈800, corresponding to a linewidth of ∼725 Hz (Qeff ≈ 2.7 × 1011) at 1555 nm. By exploiting the resulting increase in effective photon lifetime, we excite stable temporal cavity solitons and generate a low-repetition-rate frequency comb with a spacing of 580 kHz. Finally, we analyze the impact of the Raman loss-compensation mechanism, particularly its associated noise, and show that a trade-off exists between soliton excitation threshold and stability.

We theoretically investigate the dynamics of parametrically driven soliton crystals (PDSC) and their associated frequency combs in doubly resonant cavities with quadratic and cubic nonlinearities. We show that, with significant pump–signal walk-off, PDSCs emerge as robust attractors in a monostable regime, and the soliton number is set primarily by the driving strength. Pump–signal walk-off extends pump depletion from a local perturbation to a global constraint, enabling long-range soliton interactions; in combination with the pump phase, this mechanism stabilizes the crystal’s equal spacing and preserves comb coherence. Additionally, we identify a novel nonlinear state in parametric soliton crystals in which circulating solitons periodically alternate their intensities and group velocities, a phenomenon we term the {\it soliton-pursuing} states. Furthermore, due to the phase-selective nature of the optical parametric process, we show how different configurations of soliton phases determine the optical frequency combs, enabling odd-harmonic combs and subharmonic-like comb.

Théorie des lasers à mode verrouillé basés sur des modes de cavité non conventionnels: Cette thèse de doctorat porte principalement sur la dynamique et la robustesse d’un nouveau concept de verrouillage de mode dans les nanolasers semi-conducteurs ultracompacts. Un tel nanolaser présente des modes ermites-gaussiens créés par une cavité photonique harmonique pour confiner la lumière. Cela permet de mapper la cavité optique en oscillateur harmonique de mécanique quantique, avec des fréquences propres régulièrement espacées, une condition essentielle pour le verrouillage de mode. La période de verrouillage de mode est contrôlée par la conception du potentiel photonique, et non par la longueur de la cavité. Les régimes non linéaires possibles sont décrits par l’équation de Gross-Pitaevskii avec un potentiel parabolique et des termes non linéaires décrivant le gain et l’absorption. Pour étudier ces comportements dynamiques, des simulations numériques directes sont principalement mises en œuvre. Tout d’abord, la compétition de mode pour le gain entre les modes ermites et gaussiens en l’absence d’absorption saturable est étudiée. Deuxièmement, on prévoit que le verrouillage des modes se produira avec une saturation instantanée du gain et de l’absorption sur un large éventail de paramètres, correspondant à l’émergence d’une soliton dissipative. Troisièmement, dans le régime de saturation non instantanée du gain et de l’absorption, différents comportements dynamiques du nanolaser sont obtenus en faisant varier le gain et l’absorption. Ces différents régimes, y compris la commutation Q, le verrouillage de mode à commutation Q et le verrouillage de mode CW, sont décrits en détail. L’influence du facteur Henry sur le verrouillage de mode est également abordée. Quatrièmement, la robustesse du verrouillage de mode des modes ermite et gaussien au désordre de la cavité harmonique est étudiée en détail, y compris l’effet de la non-parabolicité du potentiel et les erreurs aléatoires dans la forme du potentiel.

We show that binary phase patterns of parametrically driven cavity-soliton crystals in doubly resonant cavities with second- and third-order nonlinearities can reshape frequency-combs, enabling both odd-harmonic and subharmonic-like combs.

We study the bifurcation and stability of radial symmetric solitons in one- (1D), two- (2D), and three-dimensional (3D) damped-driven Kerr cavity systems. We employ a dimension-parameterized one-dimensional framework, by imposing symmetry, where the dimension of the systems can be adjusted by a real parameter, enabling us to analyze the impact of the dimensionality increase, in a continuous fashion, on the system's dynamics. Our results applied to Kerr cavity solitons unveil how key bifurcations, such as Hopf or exponential instabilities, appear in the system and reveal that the soliton solutions tend to become more and more unstable in systems with increased dimensions. Consequently, the stability region for 2D solitons is much narrower than in 1D, and all 3D solitons are unstable against collapse in the 3D damped-driven nonlinear Schrödinger equation. Our results and methods may be applied to other physically relevant 1D, 2D, 3D systems under symmetric conditions.

While frequency comb generation in passive nonlinear optical cavities has been demonstrated in purely quadratic and Kerr platforms, the interplay between χ⁽²⁾ and χ⁽³⁾ effects is yet to be fully understood. In this work, we propose a doubly resonant AlGaAs microring design for second-harmonic Kerr-comb generation. We compute the full dispersion profile of the guided modes to describe the resulting dynamics. The doubly resonant condition implies the use of a double envelope mean-field model, and the confined field owns spectral components around both the pump and second harmonic wavelengths. The fabrication of such devices is discussed, and preliminary experimental results are presented. Due to its record nonlinear performance, we address AlGaAs as a promising platform for the generation of such novel microcomb sources.

We theoretically investigate the excitation, dynamics of parametrically driven soliton crystals and their resulting frequency combs in doubly resonant cavities with quadratic and cubic nonlinearities. We demonstrate that soliton crystal states act as strong attractors, where pump depletion and pump phase play crucial roles in their stabilization by ensuring equal soliton spacing and coherence. The number of solitons is primarily determined by driving strength. Additionally, we identify a novel nonlinear state in parametric soliton crystals in which circulating solitons periodically alternate their intensities and group velocities, a phenomenon we term the soliton-pursuing states. Furthermore, due to the phase-selective nature of the optical parametric process, we show how different configurations of soliton phases influence the optical frequency combs, which may enable generating odd harmonic combs.

In this work, we extend temporal reflection and refraction analogies from the case of singlemode optical fibers to multimode fibers. Specifically, we show that nonlinear multimode fibers provide novel degrees of freedom that permit us to control optical pulse interactions. We take advantage of the properties of pulses propagating in different modes, such as their group velocities, dispersion parameters, and effective mode areas, in the presence of the Kerr effect. Our study was carried out by numerically solving the multimode nonlinear Schrödinger equations for graded‐index optical fibers. From this analysis, we find a useful tool to obtain novel all‐optical switching and frequency conversion schemes in multimode fibers.

We study the dynamics and stability of soliton optical frequency comb generation in a dissipative, coherently pumped cavity with both second- and third-order nonlinearity. Cavity sweep simulations and linear stability analysis based on path continuation reveal the existence of bistable solitons. These families of solitons represent a continuous transition between a purely quadratic and a Kerr cavity soliton frequency comb. Perspective demonstration of these novel, to the best of our knowledge, optical sources is an ongoing relevant subject within the frequency comb community.

A coherent concatenation of multiple solitary waves may lead to a stable infrared and visible broadband filament in a ceramic YAG polycrystal. This self-trapped soliton train is leveraged to implement self-referenced multiplex coherent anti-Stokes Raman scattering (SR-M-CARS) imaging. Simulations and experiments illustrating the filamentation process and the concatenation of focusing–defocusing cycles in ceramic and crystal YAG are presented. In addition, our simulations and experiments further examine the dependence of the filamentation onset location and supercontinuum (SC) generation upon peak input power. Understanding this dependence is key for the implementation of viable CARS imaging techniques, due to the comparatively exceptional ability of YAG to generate supercontinuum that can enable higher-sensitivity imaging without delay lines.