Matteo Conforti

We report the experimental and numerical demonstration of stimulated Brillouin scattering-induced stabilization of Kerr-driven modulation instability in fiber Fabry–Perot resonators. We show that Brillouin scattering shapes the modulation instability spectrum into a stable multi–free-spectral-range cascade that is otherwise unstable in the absence of Brillouin effects. We further identify that this stabilization originates from the real part of the Brillouin response, leading to an asymmetric Kerr–Brillouin interaction governed by the relative position of the Brillouin frequency shift with respect to the cavity resonances. These results establish stimulated Brillouin scattering as an additional degree of freedom for controlling nonlinear dynamics in Kerr resonators.

We report on the interaction between stimulated Brillouin scattering and temporal cavity solitons (CSs) in doubly resonant ring resonators. Our experiments are performed in coherently driven passive optical-fiber resonators. We demonstrate that the interplay between four-wave mixing and cascade Brillouin lasing spontaneously generates patterns of CSs on a temporal grid at twice the Brillouin-shift. These patterns are shown to be highly stable owing to a long-range locking mechanism mediated by the acoustic oscillation generated by the solitons. We introduce a unified mean-field model of the cavity to describe the dynamics between the coupled forward and backward waves under coherent driving. This model reproduces the experimental results with high accuracy and explains the paracrystalline structures of the soliton pattern. Our findings significantly advance the understanding of hybrid Brillouin–Kerr optical frequency combs.

Quantitative interpretation of ultrafast pump–probe experiments requires a consistent treatment of the excitation stage, particularly under strong optical pumping where absorption saturation and interference effects become significant. We present a time-domain self-consistent framework that couples electromagnetic field propagation to semiconductor Maxwell–Bloch dynamics in thin absorbing layers. The model explicitly accounts for state filling, nonlinear absorption, and standing-wave effects without introducing phenomenological generation terms or adjustable scaling parameters. The approach is applied to low-temperature-grown GaAs layers deposited on gold mirrors, corresponding to a low-Q cavity configuration. Simulations quantitatively reproduce both the linear reflectivity oscillations as a function of layer thickness and the nonlinear saturation behavior observed experimentally. The maximum pump-induced reflectivity change is predicted from intrinsic material parameters alone. This framework provides a physically consistent basis for analyzing pump–probe measurements in multilayer absorbing structures and offers a predictive tool for the modeling and design of nonlinear semiconductor absorbers, including semiconductor saturable absorber mirrors.

We predict that dispersive shock waves can be observed in multimode fibers with a parabolic index profile despite competing with geometric parametric instability. Spatial self-imaging forces these shock waves to radiate at multiple resonant frequencies even in the absence of relevant higher-order dispersion. A simple phase-matching rule derived from a reduced model accurately describes such resonances in agreement with a full 1 + 3D model. This allows to interpret spectral reshaping of intense pulses occurring in the normal dispersion regime.

This study demonstrates that self-injection locking (SIL) of a distributed feedback (DFB) laser to a high-Q fiber Fabry Perot (FFP) resonator, fabricated with highly nonlinear fiber, allows optical frequency combs (OFC) generation with a laser power as low as 100 mW. More precisely, cavity soliton (CS) regime has been observed in this configuration, along with other types of combs. The laser stabilization using SIL is described. Then the system’s behavior is analyzed through modeling the laser’s dynamics and comparing the model results to experimental tuning curve measurements. Our findings highlight the critical role of the initial phase of the fiber link between laser and FFP in determining the stability and effectiveness of the locking process. We explore the dynamics of the nonlinear SIL process while varying the laser current, revealing the transition from modulation instability to chaotic comb states, and eventually to soliton formation as the system moves from an effective blue-detuned to an effective red-detuned regime. Notably, the inclusion of self-phase modulation (SPM) in the SIL model predicts accessibility of the narrow soliton existence range. These results highlight the potential of SIL in FFP resonators for low-power, stable OFC generation, offering a promising path forward for practical applications.

We investigate analytically, numerically and experimentally the gain-through-filtering modulation instability in a hybrid driven Kerr cavity in the normal dispersion regime including an erbium-doped fiber amplifier. We show that, thanks to the increased cavity finesse enabled by the intracavity optical gain, the injection power threshold for the modulation instability can be substantially reduced, and the energy transfer to spectral sidebands enhanced. Our findings demonstrate how to improve efficiency and bandwidth in optical frequency comb generation based on the gain-through-filtering modulation instability.

This study demonstrates that self-injection locking (SIL) of a distributed feedback (DFB) laser to a high-Q fiber Fabry Perot (FFP) resonator, fabricated with highly nonlinear fiber, allows optical frequency combs (OFC) generation with a laser power as low as 100 mW. More precisely, cavity soliton (CS) regime has been observed in this configuration, along with other types of combs. The laser stabilization using SIL is described. Then the system's behavior is analyzed through modeling the laser's dynamics and comparing the model results to experimental tuning curve measurements. Our findings highlight the critical role of the initial phase of the fiber link between laser and FFP in determining the stability and effectiveness of the locking process. We explore the dynamics of the nonlinear SIL process while varying the laser current, revealing the transition from modulation instability to chaotic comb states, and eventually to soliton formation as the system moves from an effective blue-detuned to an effective red-detuned regime. Notably, the inclusion of self-phase modulation (SPM) in the SIL model predicts accessibility of the narrow soliton existence range. These results highlight the potential of SIL in FFP resonators for low-power, stable OFC generation, offering a promising path forward for practical applications.

This paper presents a novel approach to dual-frequency comb generation utilizing a single fiber Fabry–Perot resonator, advancing the implementation of these sources in fiber-based systems. Dual-comb applications such as spectroscopy, ranging, and imaging, known for their high-resolution and rapid data acquisition capabilities, benefit significantly from the stability and coherence of optical frequency comb sources. Our method leverages the birefringent property of the resonator induced by the optical fiber to generate two orthogonally polarized optical frequency combs in a monolithic resonator. This approach allows for the generation of two different frequency combs with slightly different repetition rates, exhibiting excellent mutual coherence, making it highly relevant for dual-comb applications. The 40 nm bandwidth generated combs are induced by switching-waves in a normal dispersion fiber Fabry-Perot resonator. These comb types have the advantage of being easily generated by a pulse pumping scheme, which is employed in this study. Finally, the potential of the source is demonstrated by a proof-of-concept spectroscopy measurement.