Search results for "quantum electrodynamic"
showing 10 items of 820 documents
Fourth-order relativistic corrections to electrical first-order properties using direct perturbation theory.
2011
In this work, we present relativistic corrections to first-order electrical properties obtained using fourth-order direct perturbation theory (DPT4) at the Hartree-Fock level. The considered properties, i.e., dipole moments and electrical-field gradients, have been calculated using numerical differentiation techniques based on a recently reported DPT4 code for energies [S. Stopkowicz and J. Gauss, J. Chem. Phys. 134, 064114 (2011)]. For the hydrogen halides HX, X=F, Cl, Br, I, and At, we study the convergence of the scalar-relativistic contributions by comparing the computed DPT corrections to results from spin-free Dirac-Hartree-Fock calculations. Furthermore, since in the DPT series spin-…
Validity of rate equations for Zeeman coherences for analysis of nonlinear interaction of atoms with broadband laser radiation
2004
In this paper we, to our knowledge, for the first time obtain the rate equations for Zeeman coherences in the broad line approximation and steady-state balance equations directly from optical Bloch equations without the use of the perturbation theory. The broad line approximation allows us to use the adiabatic elimination procedure in order to eliminate the optical coherences from the optical Bloch equations, but the steady-state condition allows us to derive the balance equations straightforward. We compare our approach with the perturbation theory approach as given previously and show that our approach is more flexible in analyzing various experiments. Meanwhile we also show the validity …
Akhmediev breathers as ultra-wideband pulses
2014
We analytically calculate and discuss the radio-frequency spectrum of the so called Akhmediev breathers (ABs), a class of nonlinear solutions of the nonlinear Schrodinger equation that governs the propagation in a single mode optical fiber. We propose a practical application of ABs to the field of ultra-wideband pulse generation. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:664–667, 2014
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.
Dissipative soliton in a laser cavity: A novel concept in action
2006
International audience; The recent concept of a dissipative optical soliton sheds new light for understanding the stability of optical pulses that are generated in passively mode-locked lasers. Considering in these lasers the multiple pulsing regime of operation, the dissipative soliton concept is able to explain the great diversity of interaction behaviours that have been observed experimentally. Among the most spectacular behaviours are the formation of "soliton molecules" and "elastic-type" collisions. The dissipative soliton also explains the existence of complex limit cycles of pulsations within single pulse operation.
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…
Adiabatic approximation for quantum dissipative systems: formulation, topology and superadiabatic tracking
2010
A generalized adiabatic approximation is formulated for a two-state dissipative Hamiltonian which is valid beyond weak dissipation regimes. The history of the adiabatic passage is described by superadiabatic bases as in the nondissipative regime. The topology of the eigenvalue surfaces shows that the population transfer requires, in general, a strong coupling with respect to the dissipation rate. We present, furthermore, an extension of the Davis-Dykhne-Pechukas formula to the dissipative regime using the formalism of Stokes lines. Processes of population transfer by an external frequency-chirped pulse-shaped field are given as examples.
Experimental observation of the generation of cutoff solitons in a discreteLCnonlinear electrical line
2014
We address the problem of supratransmission of waves in a discrete nonlinear system, driven at one end by a periodic excitation at a frequency lying above the phonon band edge. In an experimental electrical transmission line made of 200 inductance-capacitance LC cells, we establish the existence of a voltage threshold for a supratransmission enabling the generation and propagation of cut-off solitons within the line. The decisive role of modulational instability in the onset and development of the process of generation of cut-off solitons is clearly highlighted. The phenomenon of dissipation is identified as being particularly harmful for the soliton generation, but we show that its impact …
Dissipative Rogue Waves Generated by Chaotic Pulse Bunching in a Mode-Locked Laser
2012
Rare events of extremely high optical intensity are experimentally recorded at the output of a mode-locked fiber laser that operates in a strongly dissipative regime of chaotic multiple-pulse generation. The probability distribution of these intensity fluctuations, which highly depend on the cavity parameters, features a long-tailed distribution. Recorded intensity fluctuations result from the ceaseless relative motion and nonlinear interaction of pulses within a temporally localized multisoliton phase. © 2012 American Physical Society.
Modal expansions in lasers outside the uniform-field limit
2003
We show that, in lasers characterized by a slow population dynamics, the expansion of the electric field on longitudinal modes is useful even beyond the uniform-field limit. The dynamical behavior of the laser above the second threshold can be well reproduced by a set of ordinary differential equations, whose integration is much faster than that of the complete Maxwell–Bloch equations. The conditions for the uniform-field limit are also clarified.