127 research outputs found
Stationary and traveling solitons via local dissipations in Bose-Einstein condensates in ring optical lattices
A model of a Bose-Einstein condensate in a ring optical lattice with atomic
dissipations applied at a stationary or at a moving location on the ring is
presented. The localized dissipation is shown to generate and stabilize both
stationary and traveling lattice solitons. Among many localized solutions, we
have generated spatially stationary quasiperiodic lattice soltions and a family
of traveling lattice solitons with two intensity peaks per potential well with
no counterpart in the discrete case. Collisions between traveling and
stationary lattice solitons as well as between two traveling lattice solitons
display a critical dependence from the lattice depth. Stable counterpropagating
solitons in ring lattices can find applications in gyroscope interferometers
with ultra-cold gases.Comment: 8 pages, 14 figure
Two-colour quantum entanglement in a singly resonant optical parametric oscillator approaching threshold
Following the analytical work of Ref. [1], a numerical analysis of squeezing and quantum entanglement in a continuous wave singly-resonant optical parametric oscillator approaching threshold is provided. The singly resonant case is mainly relevant to largely non-degenerate signal and idler modes (two-colour output). As the threshold of oscillation is approached the numerical spectra of the intensity difference confirm squeezing of quantum fluctuations and a progressive line-narrowing in the linear case. In the nonlinear case entanglement is confirmed although progressively reduced when approaching threshold with the squeezing spectra still displaying a narrowing of the spectral line. Modification of quantum entanglement approaching threshold is also evaluated via the condition of state inseparability
Interactions and Collisions of Discrete Breathers in Two-Species Bose-Einstein Condensates in Optical Lattices
The dynamics of static and travelling breathers in two-species Bose-Einstein
condensates in a one-dimensional optical lattice is modelled within the
tight-binding approximation. Two coupled discrete nonlinear Schr\"odinger
equations describe the interaction of the condensates in two cases of
relevance: a mixture of two ytterbium isotopes and a mixture of Rb and
K. Depending on their initial separation, interaction between static
breathers of different species can lead to the formation of symbiotic
structures and transform one of the breathers from a static into a travelling
one. Collisions between travelling and static discrete breathers composed of
different species are separated in four distinct regimes ranging from totally
elastic when the interspecies interaction is highly attractive to mutual
destruction when the interaction is sufficiently large and repulsive. We
provide an explanation of the collision features in terms of the interspecies
coupling and the negative effective mass of the discrete breathers.Comment: 11 pages, 10 figure
Fundamentals and applications of spatial dissipative solitons in photonic devices : [Chapter 6]
We review the properties of optical spatial dissipative solitons (SDS). These are stable, self‐localized optical excitations sitting on a uniform, or quasi‐uniform, background in a dissipative environment like a nonlinear optical cavity. Indeed, in optics they are often termed “cavity solitons.” We discuss their dynamics and interactions in both ideal and imperfect systems, making comparison with experiments. SDS in lasers offer important advantages for applications. We review candidate schemes and the tremendous recent progress in semiconductor‐based cavity soliton lasers. We examine SDS in periodic structures, and we show how SDS can be quantitatively related to the locking of fronts. We conclude with an assessment of potential applications of SDS in photonics, arguing that best use of their particular features is made by exploiting their mobility, for example in all‐optical delay lines
Subcritical patterns and dissipative solitons due to intracavity photonic crystals
Manipulation of the bifurcation structure of nonlinear optical systems via intracavity photonic crystals is demonstrated. In particular, subcritical regions between spatially periodic states are stabilized by modulations of the material's refractive index. An family of dissipative solitons within this bistability range due to the intracavity photonic crystal is identified and characterized in both one and two transverse dimensions. Nontrivial snaking of the modulated-cavity soliton solutions is also presented
Optical Rogue Waves in Vortex Turbulence
We present a spatio-temporal mechanism for producing 2D optical rogue waves
in the presence of a turbulent state with creation, interaction and
annihilation of optical vortices. Spatially periodic structures with bound
phase lose stability to phase unbound turbulent states in complex Ginzburg-
Landau and Swift-Hohenberg models with external driving. When the pumping is
high and the external driving is low, synchronized oscillations are unstable
and lead to spatio-temporal turbulence with high excursions in amplitude.
Nonlinear amplification leads to rogue waves close to turbulent optical
vortices, where the amplitude tends to zero, and to probability distribution
functions with long tails typical of extreme optical events.Comment: 5 pages, 7 figure
Stable droplets and growth laws close to the modulational instability of a domain wall
We consider the curvature driven dynamics of a domain wall separating two
equivalent states in systems displaying a modulational instability of a flat
front. We derive an amplitude equation for the dynamics of the curvature close
to the bifurcation point from growing to schrinking circular droplets. We
predict the existence of stable droplets with a radius that diverges at the
bifurcation point, where a curvature driven growth law
is obtained. Our general analytical predictions, which are valid for a wide
variety of systems including models of nonlinear optical cavities and
reaction-diffusion systems, are illustrated in the parametrically driven
complex Ginzburg-Landau equation.Comment: 4 pages, 4 figure
Phase-dependent interaction in a 4-level atomic configuration
We study a four-level atomic scheme interacting with four lasers in a
closed-loop configuration with a (diamond) geometry. We
investigate the influence of the laser phases on the steady state. We show
that, depending on the phases and the decay characteristic, the system can
exhibit a variety of behaviors, including population inversion and complete
depletion of an atomic state. We explain the phenomena in terms of multi-photon
interference. We compare our results with the phase-dependent phenomena in the
double- scheme, as studied in [Korsunsky and Kosachiov, Phys. Rev A
{\bf 60}, 4996 (1999)]. This investigation may be useful for developing
non-linear optical devices, and for the spectroscopy and laser-cooling of
alkali-earth atoms.Comment: 4 figure
Coherence build up and laser thresholds from nanolasers to macroscopic lasers
We detail the derivation of nanolaser models that include coherent and
incoherent variables and predict the existence of a laser threshold,
irrespective of cavity size and emitter number, for both single- and
multi-electron systems. The growth in photon number in the lasing mode is
driven by an increase in correlation between absorption and emission processes,
leading to the onset of self-sustained stimulated emission (laser threshold),
followed, in turn, by a correlation decrease and ending with the dominance of
coherent emission. The first-order coherence steadily increases, as
the pump grows towards the laser threshold value, and reaches unity at or
beyond threshold. The transition toward coherent emission becomes increasingly
sharp as the number of emitters and of the coupled electromagnetic cavity modes
increase, continuously connecting, in the thermodynamic limit, the physics of
nano- and macroscopic lasers at threshold. Our predictions are in remarkable
agreement with experiments whose first-order coherence measurements have so far
been explained only phenomenologically. A consistent evaluation of different
threshold indicators provides a tool for a correct interpretation of
experimental measurements at the onset of laser action.Comment: 11 pages, 5 figure
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