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Investigation of Chaotic and Spiking Dynamics in Mid-Infrared Quantum Cascade Lasers Operating Continuous-Waves and Under Current Modulation
摘要： This study investigates chaotic and spiking dynamics of mid-infrared quantum cascade lasers operating under external optical feedback and emitting at 5.5 μm and 9 μm. In order to deepen the understanding, the route to chaos is experimentally studied in the case of continuous-wave and current modulation operation. The non-linear dynamics are analyzed with bifurcation diagrams. While for quasi-continuous wave operation, chaos is found to be more complex, pure continuous wave pumping always leads to the generation of a regular spiking induced low-frequency ?uctuations dynamics. In the latter, results show that by combining external optical feedback with periodic forcing and further induced current modulation allows a better control of the chaotic dropouts. This work provides a novel insight into the development of future secure free-space communications based on quantum cascade lasers or unpredictable optical countermeasure systems operating within the two transparency atmospheric windows hence between 3 μm–5 μm and 8.5 μm–11 μm.
关键词： entrainment phenomenon,quantum cascade laser,secure communications,external optical feedback,mid-infrared photonics,Nonlinear dynamics
更新于2025-09-16 10:30:52
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[IEEE 2019 21st International Conference on Transparent Optical Networks (ICTON) - Angers, France (2019.7.9-2019.7.13)] 2019 21st International Conference on Transparent Optical Networks (ICTON) - Complex Dynamics of Long Cavity Lasers
摘要： In this paper, we will discuss the properties of long cavity frequency sweeping lasers and demonstrate various scenarios of coherence deterioration in such lasers. The long cavity lasers are known to demonstrate rich variety of dynamical regimes including formation of localised structures and transition to turbulence. The interest to frequency sweeping long cavity lasers has also recently increased due to their application for imaging and sensing. For these applications, the stability of the laser is an important parameter as it directly influences its coherence and therefore, for example, the quality of the obtained images. We investigated static, quasi static and synchronisation regimes of such lasers and analysed possible instabilities in such system. Experimentally, we considered different laser configurations which has allowed us to study the influence of the cavity length, frequency sweeping speed and the detuning. Numerically, we used a model based on a system of delayed differential equations. The numerical simulation of our model showed excellent agreement with the experimental data. In particularly, we studied the formation of dark pulses, both periodic and non-periodic, and showed that they are closely connected to Nozaki-Bekki holes previously predicted in the complex Ginzburg-Landau equation.
关键词： turbulence,optical coherence tomography,swept sources lasers,long cavity lasers,nonlinear dynamics,localised structures
更新于2025-09-12 10:27:22
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Characterization of temporal variations and feedback timescales of exhaust gas recirculation gas properties using high-speed diode laser absorption spectroscopy for next-cycle control of cyclic variability
摘要： Dilute combustion offers efficiency gains in boosted gasoline direct injection engines both through knock-limit extension and thermodynamic advantages (i.e. the effect of g on cycle efficiency), but is limited by cyclic variability at high dilution levels. Past studies have shown that the cycle-to-cycle dynamics are a combination of deterministic and stochastic effects. The deterministic causes of cyclic variations, which arise from feedback due to exhaust gas recirculation, imply the possibility of using active control strategies for dilution limit extension. While internal exhaust gas recirculation will largely provide a next-cycle effect (short-timescale feedback), the feedback of external exhaust gas recirculation will have an effect after a delay of several cycles (long timescale). Therefore, control strategies aiming to improve engine stability at dilution limit may have to account for both short- and long-timescale feedback pathways. This study shows the results of a study examining the extent to which variations in exhaust gas recirculation composition are preserved along the exhaust gas recirculation flow path and thus the relative importance and information content of the long-timescale feedback pathway. To characterize the filtering or retention of cycle-resolved feedback information, high-speed (1–5 kHz) CO2 concentration measurements were performed simultaneously at three different locations along the low-pressure external exhaust gas recirculation loop of a four-cylinder General Motors gasoline direct injection engine using a multiplexed two-color diode laser absorption spectroscopy sensor system during steady-state and transient engine operation at various exhaust gas recirculation levels. It was determined that cycle-resolved feedback propagates through internal residual gases but is filtered out by the low-pressure exhaust gas recirculation flow system and do not reach the intake manifold. Intermediate variations driven by flow rate and compositional changes are also distinguished and identified.
关键词： exhaust gas recirculation,cyclic variability,nonlinear dynamics,combustion stability,Dilute combustion
更新于2025-09-12 10:27:22
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Internal nonlinear transmission in an Yb mode-locked fiber laser through bifurcations
摘要： Mode-locked fiber lasers are rich dynamical systems that may present several different types of pulsed operating modes, depending on external control parameters such as pump power. A systematic experimental characterization of such regimes is a challenging problem. Here single pulse regimes of ytterbium mode-locked fiber laser are explored and related to the nonlinear amplitude modulation affecting the pulses inside the laser cavity. To understand the full dynamics of this system, average power measurements (slow time scale) have been performed and compared to simultaneous time-resolved measurements (fast time scale). The average nonlinear transmission resulting from the amplitude modulation is measured, allowing to relate the transitions between dynamical regimes to the system’s nonlinearity.
关键词： Mode-locked fiber laser,Transmission curve,Nonlinear dynamics
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Customizing Supercontinuum Generation Via Adaptive On-Chip Pulse Splitting
摘要： Modern optical systems increasingly rely on complex physical processes. Advanced light sources, such as supercontinuum (SC) [1], are highly sought for imaging and metrology, and are based on nonlinear dynamics where the output properties must often finely match target performance characteristics. However, in these systems, the availability of control parameters and the means to adjust them in a versatile manner are usually limited. Moreover, finding the ideal parameters for a specific application can become inherently complex. Here, we use an actively-controlled photonic chip to prepare and manipulate patterns of femtosecond optical pulses seeding supercontinuum generation [1]. Taking advantage of machine learning concepts [2], we exploit this access to an enhanced and tunable parameter space and experimentally demonstrate the customization of nonlinear interactions responsible for tailoring supercontinuum properties [3].
关键词： femtosecond optical pulses,supercontinuum generation,photonic chip,machine learning,nonlinear dynamics
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Fermi-Pasta-Ulam-Tsingou Recurrence in Spatial Optical Dynamics
摘要： Celebrated as the Fermi-Pasta-Ulam-Tsingou (FPUT) problem, the reappearance of initial conditions in unstable and chaotic systems is one of the most controversial phenomena in nonlinear dynamics. Integrable models predict recurrence as exact solutions [1], but the difficulties involved in upholding integrability for a long dynamics has not allowed a quantitative experimental validation. Evidences of the recurrence of states have been reported from deep water waves [2] to optical fibers [3]. However, the observation of the FPUT dynamics as predicted by exact solutions of an underlying integrable model remains an open challenge. Here, we report the observation of the FPUT recurrence in spatial nonlinear optics and provide evidence that the recurrent behavior is ruled by the exact solution of the Nonlinear Schrodinger Equation [4]. We exploit a three-waves interferometric setup [Fig. 1(a)] to finely tune amplitude and phase of the single-mode input perturbation propagating in a pumped photorefractive medium [5]. We reveal how the unstable mode manifests the Akhmediev breathers (AB) profile [Fig.1(c)] and undergoes several growth and decay cycles [Fig. 1(b)] whose partial-period and phase-shift are determined by the initial excitation in remarkable agreement with the analytic NLSE theory [Fig.1(d-e)]. The deterministic properties of the return cycle allows us to achieve one of the basic aspirations of nonlinear dynamics: the reconstruction, after several return cycles, of the exact initial condition of the system [Fig. 1(f)], ultimately proving that the complex evolution can be accurately predicted in experimental conditions. This results extends predictive approaches to unstable wave regimes and maps a strategy to achieve the control of rogue waves [6] in environmental conditions. In general, our findings shed light on the foundations of the FPUT problem and represent a unique test for nonlinear wave theory, with broad implications in nonlinear optics, hydrodynamics and beyond.
关键词： Nonlinear Schrodinger Equation,spatial optical dynamics,Akhmediev breathers,Fermi-Pasta-Ulam-Tsingou recurrence,nonlinear dynamics
更新于2025-09-11 14:15:04
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Delocalized Nonlinear Vibrational Modes in Graphene: Second Harmonic Generation and Negative Pressure
摘要： With the help of molecular dynamics simulations, delocalized nonlinear vibrational modes (DNVM) in graphene are analyzed. Such modes are dictated by the lattice symmetry, they are exact solutions to the atomic equations of motion, regardless the employed interatomic potential and for any mode amplitude (though for large amplitudes they are typically unstable). In this study, only one- and two-component DNVM are analyzed, they are reducible to the dynamical systems with one and two degrees of freedom, respectively. There exist 4 one-component and 12 two-component DNVM with in-plane atomic displacements. Any two-component mode includes one of the one-component modes. If the amplitudes of the modes constituting a two-component mode are properly chosen, periodic in time vibrations are observed for the two degrees of freedom at frequencies ω and 2ω, that is, second harmonic generation takes place. For particular DNVM, the higher harmonic can have frequency nearly two times larger than the maximal frequency of the phonon spectrum of graphene. Excitation of some of DNVM results in the appearance of negative in-plane pressure in graphene. This counterintuitive result is explained by the rotational motion of carbon hexagons. Our results contribute to the understanding of nonlinear dynamics of the graphene lattice.
关键词： molecular dynamics,nonlinear dynamics,second harmonic generation,delocalized nonlinear vibrational mode,graphene,negative pressure
更新于2025-09-10 09:29:36
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Wide-band high absorption electromagnetic absorber with Chaos patterned surface
摘要： A resistive metasurface surface featured by Rossler Chaos reaction-diffusion system patterns is proposed and realized in a wideband electromagnetic absorber. The chaos surface consists of units with both random shapes and dimensions. Simulation results show absorption phenomenon and correlation function analysis indicates new wave-absorbing mode can be generated when correlation of the edges of the chaos patterns matches geometrical size of chaos units. Experimental results indicate unconventional bandwidth ratio with reflectivity lower than -10dB, -15dB, -19dB reaches 96.84%, 80.1% and 56.1%, respectively. High absorption nature makes this structure has application potential in modern anechoic chamber or other electromagnetic wave absorbers.
关键词： metasurface,chaos pattern,disordered surface,nonlinear dynamics,absorbing metamaterial
更新于2025-09-04 15:30:14