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1.
Phys Rev Lett ; 118(4): 044102, 2017 Jan 27.
Article in English | MEDLINE | ID: mdl-28186807

ABSTRACT

A stable nonlinear wave packet, self-localized in all three dimensions, is an intriguing and much sought after object in nonlinear science in general and in nonlinear photonics in particular. We report on the experimental observation of mode-locked spatial laser solitons in a vertical-cavity surface-emitting laser with frequency-selective feedback from an external cavity. These spontaneously emerging and long-term stable spatiotemporal structures have a pulse length shorter than the cavity round-trip time and may pave the way to completely independent cavity light bullets.

2.
Phys Rev Lett ; 114(17): 173903, 2015 May 01.
Article in English | MEDLINE | ID: mdl-25978236

ABSTRACT

Theoretical analysis of the optomechanics of degenerate bosonic atoms with a single feedback mirror shows that self-structuring occurs only above an input threshold that is quantum mechanical in origin. This threshold also implies a lower limit to the size (period) of patterns that can be produced in a condensate for a given pump intensity. These thresholds are interpreted as due to the quantum rigidity of Bose-Einstein condensates, which has no classical counterpart. Above the threshold, the condensate self-organizes into an ordered supersolid state with a spatial period self-selected by optical diffraction.

3.
Philos Trans A Math Phys Eng Sci ; 372(2027)2014 Oct 28.
Article in English | MEDLINE | ID: mdl-25246676

ABSTRACT

We study non-equilibrium spatial self-organization in cold atomic gases, where long-range spatial order spontaneously emerges from fluctuations in the plane transverse to the propagation axis of a single optical beam. The self-organization process can be interpreted as a synchronization transition in a fully connected network of fictitious oscillators, and described in terms of the Kuramoto model.

4.
Phys Rev Lett ; 112(4): 043901, 2014 Jan 31.
Article in English | MEDLINE | ID: mdl-24580450

ABSTRACT

We investigate transverse symmetry-breaking instabilities emerging from the optomechanical coupling between light and the translational degrees of freedom of a collisionless, damping-free gas of cold, two-level atoms. We develop a kinetic theory that can also be mapped on to the case of an electron plasma under ponderomotive forces. A general criterion for the existence and spatial scale of transverse instabilities is identified; in particular, we demonstrate that monotonically decreasing velocity distribution functions are always unstable.

5.
Opt Express ; 21(22): 26144-9, 2013 Nov 04.
Article in English | MEDLINE | ID: mdl-24216838

ABSTRACT

We investigate the coupled dynamics of light and cold atoms in a unidirectional ring cavity, in the regime of low saturation and linear single-atom response. As the dispersive opto-mechanical coupling between light and the motional degrees of freedom of the atoms makes the dynamics nonlinear, we find that localized, nonlinearity-sustained and bistable structures can be encoded in the atomic density by means of appropriate control beams.

6.
Phys Rev Lett ; 108(21): 213904, 2012 May 25.
Article in English | MEDLINE | ID: mdl-23003255

ABSTRACT

Defects due to growth fluctuations in broad-area semiconductor lasers induce pinning and frequency shifts of spatial laser solitons. The effects of defects on the interaction of two solitons are considered in lasers with frequency-selective feedback both theoretically and experimentally. We demonstrate frequency and phase synchronization of paired laser solitons as their detuning is varied. In both theory and experiment the locking behavior is well described by the Adler model for the synchronization of coupled oscillators.

7.
Phys Rev E Stat Nonlin Soft Matter Phys ; 84(3 Pt 2): 036213, 2011 Sep.
Article in English | MEDLINE | ID: mdl-22060481

ABSTRACT

We use the cubic complex Ginzburg-Landau equation linearly coupled to a dissipative linear equation as a model for lasers with an external frequency-selective feedback. This system may also serve as a general pattern-formation model in media driven by an intrinsic gain and selective feedback. While, strictly speaking, the approximation of the laser nonlinearity by a cubic term is only valid for small field intensities, it qualitatively reproduces results for dissipative solitons obtained in models with a more complex nonlinearity in the whole parameter region where the solitons exist. The analysis is focused on two-dimensional stripe-shaped and vortex solitons. An analytical expression for the stripe solitons is obtained from the known one-dimensional soliton solution, and its relation with vortex solitons is highlighted. The radius of the vortices increases linearly with their topological charge m, therefore the stripe-shaped soliton may be interpreted as the vortex with m=∞, and, conversely, vortex solitons can be realized as unstable stripes bent into stable rings. The results for the vortices are applicable for a broad class of physical systems.

8.
Opt Express ; 18(9): 8859-66, 2010 Apr 26.
Article in English | MEDLINE | ID: mdl-20588731

ABSTRACT

We report on the existence, stability and dynamical properties of two-dimensional self-localized vortices with azimuthal numbers up to 4 in a simple model for lasers with frequency-selective feedback.We build the full bifurcation diagram for vortex solutions and characterize the different dynamical regimes. The mathematical model used, which consists of a laser rate equation coupled to a linear equation for the feedback field, can describe the spatiotemporal dynamics of broad area vertical cavity surface emitting lasers with external frequency selective feedback in the limit of zero delay.

9.
Phys Rev E Stat Nonlin Soft Matter Phys ; 78(1 Pt 2): 016212, 2008 Jul.
Article in English | MEDLINE | ID: mdl-18764040

ABSTRACT

In this paper, we analyze a model of broad area vertical-cavity surface-emitting lasers subjected to frequency-selective optical feedback. In particular, we analyze the spatio-temporal regimes arising above threshold and the existence and dynamical properties of cavity solitons. We build the bifurcation diagram of stationary self-localized states, finding that branches of cavity solitons emerge from the degenerate Hopf bifurcations marking the homogeneous solutions with maximal and minimal gain. These branches collide in a saddle-node bifurcation, defining a maximum pump current for soliton existence that lies below the threshold of the laser without feedback. The properties of these cavity solitons are in good agreement with those observed in recent experiments.

10.
Phys Rev Lett ; 100(1): 013907, 2008 Jan 11.
Article in English | MEDLINE | ID: mdl-18232769

ABSTRACT

The realization of a cavity soliton laser using a vertical-cavity surface-emitting semiconductor gain structure coupled to an external cavity with a frequency-selective element is reported. All-optical control of bistable solitonic emission states representing small microlasers is demonstrated by injection of an external beam. The control scheme is phase insensitive and hence expected to be robust for all-optical processing applications. The mobility of these structures is also demonstrated.

11.
Phys Rev Lett ; 99(15): 153902, 2007 Oct 12.
Article in English | MEDLINE | ID: mdl-17995167

ABSTRACT

Two-dimensional fronts and coarsening dynamics with a t{1/2} power law are analyzed experimentally and theoretically in a nonlinear optical system of a sodium vapor cell with single-mirror feedback. Modifications of the t{1/2} power law are observed in the vicinity of a modulational instability leading to the formation of spatial solitons of different sizes. The experimental and numerical observations give direct evidence for the locking of fronts as the mechanism of soliton formation. A phenomenological equation for the dynamics of the domain radius explains the observed behavior.

12.
Phys Rev Lett ; 99(10): 104503, 2007 Sep 07.
Article in English | MEDLINE | ID: mdl-17930391

ABSTRACT

In spatially extended Turing-unstable systems, parameter variation should, in theory, produce only fully developed patterns. In experiment, however, localized patterns or solitons sitting on a smooth background often appear. Addition of a nonlocal nonlinearity can resolve this discrepancy by tilting the "snaking" bifurcation diagram characteristic of such problems.

13.
Chaos ; 17(3): 037115, 2007 Sep.
Article in English | MEDLINE | ID: mdl-17903022

ABSTRACT

The existence of localized structures, including so-called cavity solitons, in driven optical systems is discussed. In theory, they should exist only below the threshold of a subcritical modulational instability, but in experiment they often appear spontaneously on parameter variation. The addition of a nonlocal nonlinearity may resolve this discrepancy by tilting the "snaking" bifurcation diagram characteristic of such problems.

14.
Phys Rev E Stat Nonlin Soft Matter Phys ; 75(5 Pt 2): 056208, 2007 May.
Article in English | MEDLINE | ID: mdl-17677149

ABSTRACT

Spatially self-localized states have been found in a model of vertical-cavity surface-emitting lasers with frequency-selective optical feedback. The structures obtained differ from most known dissipative solitons in optics in that they are localized traveling waves. The results suggest a route to realization of a cavity soliton laser using standard semiconductor laser designs.

15.
Phys Rev Lett ; 99(25): 253601, 2007 Dec 21.
Article in English | MEDLINE | ID: mdl-18233519

ABSTRACT

We investigate the effect of pump phase noise on the collective backscattering of light by a cold, collisionless atomic gas. We show that for a partially coherent pump field, the growth rate of the backscattered field is reduced relative to that for a coherent pump, but the backscattered intensity can be increased. Our results demonstrate that fluctuations and noise can play a counterintuitive role in nonlocally coupled many-body systems.

16.
Phys Rev E Stat Nonlin Soft Matter Phys ; 66(4 Pt 2): 046605, 2002 Oct.
Article in English | MEDLINE | ID: mdl-12443347

ABSTRACT

We present a Fourier-transform based, computer-assisted, technique to find the stationary solutions of a model describing a saturable absorber in a driven optical cavity. We illustrate the method by finding essentially exact hexagonal and roll solutions as a function of wave number and of the input pump. The method, which is widely applicable, also allows the determination of the domain of stability (Busse balloon) of the pattern, and sheds light on the mechanisms responsible for any instability. To show the usefulness of our numerical technique, we describe cracking and shrinking patches of patterns in a particular region of parameter space.

17.
Phys Rev E Stat Nonlin Soft Matter Phys ; 66(4 Pt 2): 046606, 2002 Oct.
Article in English | MEDLINE | ID: mdl-12443348

ABSTRACT

We apply quasi-exact numerical techniques to the calculation of stationary one- and two-dimensional, bound multipeaked cavity soliton solutions of a model describing a saturable absorber in a driven optical cavity. We calculate the existence and stability domains of a wide range of such states and determine the perturbative eigenmodes that cause loss of stability. We relate the existence of N-peaked states to the locking range between patterned and homogeneous solutions, as a function of two parameters.

18.
Phys Rev E Stat Nonlin Soft Matter Phys ; 66(3 Pt 2B): 036607, 2002 Sep.
Article in English | MEDLINE | ID: mdl-12366280

ABSTRACT

We demonstrate the existence of both bright and dark spontaneously moving spatial solitons in a model of a semiconductor microcavity. The motion is caused by temperature-induced changes in the cavity detuning and arises through an instability of the stationary soliton solution above some threshold. An order parameter equation is derived for the moving solitons and is used to explain their behavior in the presence of externally imposed parameter modulations. The existence of two-dimensional moving solitons is demonstrated and an example given of their interaction.

19.
Phys Rev E Stat Nonlin Soft Matter Phys ; 64(5 Pt 2): 056618, 2001 Nov.
Article in English | MEDLINE | ID: mdl-11736127

ABSTRACT

We demonstrate that in the parametrically driven Ginzburg-Landau equation arbitrarily small nongradient corrections lead to qualitative differences in the dynamical properties of domain walls in the vicinity of the transition from rest to motion. These differences originate from singular rotation of the eigenvector governing the transition. We present analytical results on the stability of Ising walls, deriving explicit expressions for the critical eigenvalue responsible for the transition from rest to motion. We then develop a weakly nonlinear theory to characterize the singular character of the transition and analyze the dynamical effects of spatial inhomogeneities.

20.
Phys Rev E Stat Nonlin Soft Matter Phys ; 63(6 Pt 2): 066209, 2001 Jun.
Article in English | MEDLINE | ID: mdl-11415208

ABSTRACT

Mean field models of spatially extended degenerate optical parametric oscillators possess one-dimensional stable domain wall solutions in the presence of diffraction. We characterize these structures as spiral heteroclinic connections and study the spatial frequency of the local oscillations of the signal intensity which distinguish them from diffusion kinks. Close to threshold, at resonance or with positive detunings, the dynamics of two-dimensional diffractive domain walls is ruled by curvature effects with a t(1/2) growth law, and coalescence of domains is observed. In this regime, we show how to stabilize regular and irregular distributions of two-dimensional domain walls by injection of a helical wave at the pump frequency. Further above threshold the shrinking of domains of one phase embedded in the other is stopped by the interaction of the oscillatory tails of the domain walls, leading to cavity solitons surrounded by a characteristic dark ring. We investigate the nature and stability of these localized states, provide evidence of their solitonic character, show that they correspond to spiral homoclinic orbits and find that their threshold of appearance lowers with increasing pump cavity finesse.

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