Search results for "PLASMA"
showing 10 items of 4043 documents
Complexes and Molecules of Dissipative Solitons in Mode-Locked Lasers
2009
Pulse-pulse interaction is a major issue in the development of high-repetition rate fiber laser sources or soliton-based optical transmission lines. The design of a suitable level of nonlinear dissipation, through nonlinear filters or saturable absorbers for instance, is able to improve significantly the stability of multiple pulse operation. The concept of a dissipative soliton has become an important tool for the exploration and the analysis of the multiple pulse dynamics, with mode-locked lasers and regenerated transmission lines as important applications [1,2]. Above all, the study of dissipative solitons has become a fertile area of nonlinear science with multidisciplinary implications…
Catastrophic process of coherence degradation
2018
We predict a catastrophic process of coherence degradation characterized by a virtually unlimited spectral broadening of the waves. This effect is described by self-similar solutions of the kinetic equations inherent to the wave turbulence theory.
Temporal dynamics of incoherent waves in noninstantaneous response nonlinear Kerr media
2012
International audience; We consider the temporal evolution of an incoherent optical wave that propagates in a noninstantaneous response nonlinear medium, such as single mode optical fibers. In contrast with the expected Raman-like spectral redshift due to a delayed nonlinear response, we show that a highly noninstantaneous response leads to a genuine modulational instability of the incoherent optical wave. We derive a Vlasov-like kinetic equation that provides a detailed description of this process of incoherent modulational instability in the temporal domain.
Self-polarization effect in the middle point of an optical fiber
2019
In this paper, we report both numerically and experimentally an unexpected phenomenon of self-polarization occurring in the middle point of an isotropic optical fiber when two uncorrelated partially polarized waves are simultaneously injected at the ends of the fiber. More precisely, we demonstrate that two counterpropagating waves of equal intensity exhibit a spontaneous organization of their polarization states around two pools of attraction just in the middle point of propagation, and then both recover a partially polarized state at their respective fiber outputs. The self-polarization effect then remains hidden within the optical fiber in the sense that no apparent sign of this process …
Higher-Order Modulation Instability in Nonlinear Fiber Optics
2011
International audience; We report theoretical, numerical, and experimental studies of higher-order modulation instability in the focusing nonlinear Schrödinger equation. This higher-order instability arises from the nonlinear superposition of elementary instabilities, associated with initial single breather evolution followed by a regime of complex, yet deterministic, pulse splitting. We analytically describe the process using the Darboux transformation and compare with experiments in optical fiber. We show how a suitably low frequency modulation on a continuous wave field induces higher-order modulation instability splitting with the pulse characteristics at different phases of evolution r…
Nonequilibrated oscillations of coherence in coupled nonlinear wave systems
2006
International audience; We show that a conservative system of a pair of coupled incoherent nonlinear waves exhibits huge oscillations of coherence, which are characterized by a recurrent transfer of noise fluctuations between the coupled waves. This sustained oscillatory behavior is in contradiction with the expected irreversible evolution towards equilibrium. As a consequence, the process of coherence transfer is characterized by a reduction of nonequilibrium entropy, which violates the H theorem of entropy growth inherent to the kinetic theory.
Wave-turbulence approach of supercontinuum generation: Influence of self-steepening and higher-order dispersion
2009
International audience; We analyze the influence of self-steepening and higher-order dispersion on the process of optical wave thermalization. This study is aimed at developing a thermodynamic formulation of supercontinuum generation in photonic crystal fibers. In the highly nonlinear regime of supercontinuum generation, the optical field exhibits a turbulent dynamics that may be described by the kinetic wave theory. In this respect, the phenomenon of spectral broadening inherent to supercontinuum generation may be interpreted as a natural process of thermalization, which is characterized by an irreversible evolution of the optical field toward a thermodynamic equilibrium state. The numeric…
Rogue waves, rational solitons and wave turbulence theory
2011
International audience; Considering a simple one dimensional nonlinear Schrödinger optical model, we study the existence of rogue wave events in the highly incoherent state of the system and compare them with the recently identified hierarchy of rational soliton solutions. We show that rogue waves can emerge in the genuine turbulent regime and that their coherent deterministic description provided by the rational soliton solutions is compatible with an accurate statistical description of the random wave provided by the wave turbulence theory. Furthermore, the simulations reveal that even in the weakly nonlinear regime, the nonlinearity can play a key role in the emergence of an individual r…
Field-free molecular alignment of CO2 mixtures in presence of collisional relaxation
2008
The present work explores the extension of the concept of short-pulse-induced alignment to dissipative environments within quantum mechanical density matrix formalism (Liouville equation) from the weak to the strong field regime. This is illustrated within the example of the CO2 molecule in mixture with Ar and He, at room temperature, for which a steep decrease of the alignment is observed at moderate pressure because of the collisional relaxation. The field-free alignment is measured by a polarization technique where the degree of alignment is monitored in the time domain by measuring the resulting transient birefringence with a probe pulse Raman induced polarization spectroscopy (RIPS) Co…
Hyperfine transitions in the first overtone mode of hydrogen deuteride
2020
Beyond the metrology and computational challenges associated with molecular hydrogen, key data are expected to assess the physics of simple molecular systems, and even the new physics beyond the standard model. To assist the deciphering of Doppler-free spectra obtained at very high accuracy ($\ensuremath{\sim}{10}^{\ensuremath{-}9})$, we report on hyperfine transitions of HD in the lowest vibrational levels of the ground electronic state. Using the spin-rotation, nuclear spin-spin, and quadrupolar hyperfine couplings determined by means of high-level quantum-chemical calculations, the hyperfine energy levels and the associated line intensity have been obtained by using tensorial momentum al…