arXiv subjects

Yaroslav V. Kartashov

Publications and source records attributed to Yaroslav V. Kartashov.

At least 181 records · Page 10Linked to original sources

arXiv2012

Anderson localization in Bragg-guiding arrays with negative defects

We show that Anderson localization is possible in waveguide arrays with periodically-spaced defect waveguides having lower refractive index. Such localization is mediated by Bragg reflection, and it takes place even if diagonal or off-diagonal disorder affects only defect waveguides. For off-diagonal disorder the localization degree of the intensity distributions monotonically grows with increasing disorder. In contrast, under appropriate conditions, increasing diagonal disorder may result in weaker localization.

physics.optics↗

arXiv2012

Stable surface solitons in truncated complex potentials

We show that surface solitons in the one-dimensional nonlinear Schrödinger equation with truncated complex periodic potential can be stabilized by linear homogeneous losses, which are necessary to balance gain in the near-surface channel arising from the imaginary part of potential. Such solitons become stable attractors when the strength of homogeneous losses acquires values from a limited interval and they exist in focusing and defocusing media. The domains of stability of surface solitons shrink with increase of the amplitude of imaginary part of complex potential.

physics.optics↗

arXiv2012

Stable bright and vortex solitons in photonic crystal fibers with inhomogeneous defocusing nonlinearity

We predict that a photonic crystal fiber whose strands are filled with a defocusing nonlinear medium can support stable bright and also vortex solitons if the strength of the defocusing nonlinearity grows toward the periphery of the fiber. The domains of soliton existence depend on the transverse growth rate of the filling nonlinearity and nonlinearity of the core. Remarkably, solitons exist even when the core material is linear.

physics.optics↗

arXiv2012

Vortex soliton tori with multiple nested phase singularities in dissipative media

We show the existence of stable two- and three-dimensional vortex solitons carrying multiple, spatially separated, single-charge topological dislocations nested around a vortex-ring core. Such new nonlinear states are supported by elliptical gain landscapes in focusing nonlinear media with two-photon absorption. The separation between the phase dislocations is dictated mostly by the geometry of gain landscape and it only slightly changes upon variation of the gain or absorption strength.

physics.optics↗

arXiv2012

Solitons supported by spatially inhomogeneous nonlinear losses

We uncover that, in contrast to the common belief, stable dissipative solitons exist in media with uniform gain in the presence of nonuniform cubic losses, whose local strength grows with coordinate x (in one dimension) faster than |x|. The spatially-inhomogeneous absorption also supports new types of solitons, that do not exist in uniform dissipative media. In particular, single-well absorption profiles give rise to spontaneous symmetry breaking of fundamental solitons in the presence of uniform focusing nonlinearity, while stable dipoles are supported by double-well absorption landscapes. Dipole solitons also feature symmetry breaking, but under defocusing nonlinearity.

nlin.PS↗

arXiv2012

Topological light bullets supported by spatio-temporal gain

We reveal that the competition between diffraction, cubic nonlinearity, two-photon absorption, and gain localized in both space and time results in arrest of collapse, suppression of azimuthal modula-tion instabilities for spatiotemporal wavepackets, and formation of stable three-dimensional light bul-lets. We show that Gaussian spatiotemporal gain landscapes support bright, fundamental light bullets, while gain landscapes featuring a ring-like spatial and a Gaussian temporal shapes may support stable vortex bullets carrying topological phase dislocations.

physics.optics↗

arXiv2011

Quasi-one-dimensional flow of polariton condensate past an obstacle

Nonlinear wave patterns generated by the flow of polariton condensate past an obstacle are studied for quasi-one-dimensional microcavity geometry. It is shown that pumping and nonlinear damping play a crucial role in this process leading to sharp differences in subsonic and supersonic regimes. Subsonic flows result in a smooth disturbance of the equilibrium condensate around the obstacle whereas supersonic flow generates a dispersive shock wave in the flow upstream the obstacle and a long smooth downstream tail. Main characteristics of the wave pattern are calculated analytically and analytical results are in excellent agreement with the results of numerical simulations. The conditions for existence of stationary wave patterns are determined numerically.

cond-mat.quant-gas↗

arXiv2011

Stationary one-dimensional dispersive shock waves

We address shock waves generated upon the interaction of tilted plane waves with negative refractive index defect in defocusing media with linear gain and two-photon absorption. We found that in contrast to conservative media where one-dimensional dispersive shock waves usually exist only as nonstationary objects expanding away from defect or generating beam, the competition between gain and two-photon absorption in dissipative medium results in the formation of localized stationary dispersive shock waves, whose transverse extent may considerably exceed that of the refractive index defect. One-dimensional dispersive shock waves are stable if the defect strength does not exceed certain critical value.

physics.optics↗

arXiv2011

Light localization in nonuniformly randomized lattices

We address Anderson localization of light in disordered optical lattices where the disorder strength varies across the transverse direction. Such variation changes the preferred domains where formation of localized eigenmodes is most probable, hence drastically impacting light localization properties. Thus, step-like disorder results in formation of modes with different decay rates at both sides of the interface, while a smoothly varying disorder yields appearance of modes that are extended within weakly disordered domains and rapidly fade away in strongly disordered domains.

physics.optics↗

arXiv2011

Self-trapping and splitting of bright vector solitons under inhomogeneous defocusing nonlinearities

We show that bimodal systems with a spatially nonuniform defocusing cubic nonlinearity, whose strength grows toward the periphery, can support stable two-component solitons. For a sufficiently strong XPM interaction, vector solitons with overlapping components become unstable, while stable families of solitons with spatially separated components emerge. Stable complexes with separated components may be composed not only of fundamental solitons, but of multipoles too.

physics.optics↗

arXiv2011

Vortex twins and anti-twins supported by multi-ring gain landscapes

We address the properties of multi-vortex soliton complexes supported by multi-ring gain landscapes in focusing Kerr nonlinear media with strong two-photon absorption. Stable complexes incorporating two, three, or four vortices featuring opposite or identical topological charges are shown to exist. In the simplest geometries with two amplifying rings vortex twins with equal topological charges exhibit asymmetric intensity distributions, while vortex anti-twins may be symmetric or asymmetric, depending on the gain level and separation between rings. Different arrangements of amplifying rings allow generation of stable multi-vortex soliton complexes with various topologies, with twins and anti-twins as building blocks.

physics.optics↗

arXiv2011

Bright solitons from defocusing nonlinearities

We report that defocusing cubic media with spatially inhomogeneous nonlinearity, whose strength increases rapidly enough toward the periphery, can support stable bright localized modes. Such nonlinearity landscapes give rise to a variety of stable solitons in all three dimensions, including 1D fundamental and multihump states, 2D vortex solitons with arbitrarily high topological charges, and fundamental solitons in 3D. Solitons maintain their coherence in the state of motion, oscillating in the nonlinear potential as robust quasi-particles and colliding elastically. In addition to numerically found soliton families, particular solutions are found in an exact analytical form, and accurate approximations are developed for the entire families, including moving solitons.

physics.optics↗

arXiv2011

Algebraic bright and vortex solitons in defocusing media

We demonstrate that spatially inhomogeneous defocusing nonlinear landscapes with the nonlinearity coefficient growing toward the periphery as [1+abs(r)]**a support one- and two-dimensional fundamental and higher-order bright solitons, as well as vortex solitons, with algebraically decaying tails. The energy flow of the solitons converges as long as nonlinearity growth rate exceeds the dimensionality, i.e., a>D. Fundamental solitons are always stable, while multipoles and vortices are stable if the nonlinearity growth rate is large enough.

physics.optics↗

arXiv2011

Solitons in geometric potentials

We show that the geometrically-induced potential existing in undulated slab waveguides dramatically affects the properties of solitons. In particular, whereas solitons residing in the potential maxima do not feature power thresholds and are stable, their counterparts residing in the potential minima are unstable and may exhibit a power threshold for their existence. Additionally, the geometric potential is shown to supports stable multipole solitons that cannot be supported by straight waveguides. Finally, the geometric potential results in the appearance of the effective barriers that prevent transverse soliton motion.

physics.optics↗

arXiv2011

Dynamical light control in longitudinally modulated segmented waveguide arrays

We address light propagation in segmented waveguide arrays where the refractive index is longitudinally modulated with an out-of-phase modulation in adjacent waveguides, so that the coupling strength varies along propagation direction. Thus in resonant segments coupling may be inhibited hence light remains localized, while in detuned segments coupling results in complex switching scenarios that may be controlled by stacking several resonant and nonresonant segments. By tuning the modulation frequency and lengths of waveguide segments one may control the distribution of light among the output guides, including loca-lizing all light in the selected output channel.

physics.optics↗

arXiv2011

General quasi-non-spreading linear three-dimensional wave-packets

We introduce a general approach for generation of sets of three-dimensional quasi-non-spreading wavepackets propagating in linear media, also referred to as linear light bullets. The spectrum of rigorously non-spreading wavepackets in media with anomalous group velocity dispersion is localized on the surface of a sphere, thus drastically restricting the possible wavepacket shapes. However, broadening slightly the spectrum affords the generation of a large variety of quasi-non-spreading distributions featuring complex topologies and shapes in space and time that are of interest in different areas, such as biophysics or nanosurgery. Here we discuss the method and show several illustrative examples of its potential.

physics.optics↗

arXiv2011

Stripe-like quasi-nondiffracting optical lattices

We introduce stripe-like quasi-nondiffracting lattices that can be generated via spatial spectrum engineering. The complexity of the spatial shapes of such lattices and the distance of their almost diffractionless propagation depend on the width of their ring-like spatial spectrum. Stripe-like lattices are extended in one direction and are localized in the orthogonal one, thereby creating either straight or curved in any desired fashion optically-induced channels that may be used for optical trapping, optical manipulation, or optical lattices for quantum and nonlinear optics applications. As an illustrative example, here we show their potential for spatial soliton control. Complex networks consisting of several intersecting or joining stripe-like lattices suited to a particular application may also be constructed.

physics.optics↗

arXiv2011

Solitons in PT-symmetric nonlinear lattices

Existence of localized modes supported by the PT-symmetric nonlinear lattices is reported. The system considered reveals unusual properties: unlike other typical dissipative systems it possesses families (branches) of solutions, which can be parametrized by the propagation constant; relatively narrow localized modes appear to be stable, even when the conservative nonlinear lattice potential is absent; finally, the system supports stable multipole solutions.

nlin.PS↗