439 research outputs found
Wave patterns generated by a flow of two-component Bose-Einstein condensate with spin-orbit interaction past a localized obstacle
It is shown that spin-orbit interaction leads to drastic changes in wave
patterns generated by a flow of two-component Bose-Einstein condensate (BEC)
past an obstacle. The combined Rashba and Dresselhaus spin-orbit interaction
affects in different ways two types of excitations---density and polarization
waves---which can propagate in a two-component BEC. We show that the density
and polarization "ship wave" patterns rotate in opposite directions around the
axis located at the obstacle position and the angle of rotation depends on the
strength of spin-orbit interaction. This rotation is accompanied by narrowing
of the Mach cone. The influence of spin-orbit coupling on density solitons and
polarization breathers is studied numerically.Comment: 5 pages, 3 figure
Stable one-dimensional periodic waves in Kerr-type saturable and quadratic nonlinear media
We review the latest progress and properties of the families of bright and
dark one-dimensional periodic waves propagating in saturable Kerr-type and
quadratic nonlinear media. We show how saturation of the nonlinear response
results in appearance of stability (instability) bands in focusing (defocusing)
medium, which is in sharp contrast with the properties of periodic waves in
Kerr media. One of the key results discovered is the stabilization of
multicolor periodic waves in quadratic media. In particular, dark-type waves
are shown to be metastable, while bright-type waves are completely stable in a
broad range of energy flows and material parameters. This yields the first
known example of completely stable periodic wave patterns propagating in
conservative uniform media supporting bright solitons. Such results open the
way to the experimental observation of the corresponding self-sustained
periodic wave patterns.Comment: 29 pages, 10 figure
Nonlinearity-induced broadening of resonances in dynamically modulated couplers
We report the observation of nonlinearity-induced broadening of resonances in
dynamically modulated directional couplers. When the refractive index of the
guiding channels in the coupler is harmonically modulated along the propagation
direction and out-of-phase in two channels, coupling can be completely
inhibited at resonant modulation frequencies. We observe that nonlinearity
broadens such resonances and that localization can be achieved even in detuned
systems at power levels well below those required in unmodulated couplers.Comment: 14 pages, 4 figures, to appear in Optics Letter
Observation of surface solitons in chirped waveguide arrays
We report the observation of surface solitons in chirped semi-infinite
waveguide arrays whose waveguides exhibit exponentially decreasing refractive
indices. We show that the power threshold for surface wave formation decreases
with an increase of the array chirp and that for sufficiently large chirp
values linear surface modes are supported.Comment: 12 pages, 3 figures, to appear in Optics Letter
Dissipative surface solitons in periodic structures
We report dissipative surface solitons forming at the interface between a
semi-infinite lattice and a homogeneous Kerr medium. The solitons exist due to
balance between amplification in the near-surface lattice channel and
two-photon absorption. The stable dissipative surface solitons exist in both
focusing and defocusing media, when propagation constants of corresponding
states fall into a total semi-infinite and or into one of total finite gaps of
the spectrum (i.e. in a domain where propagation of linear waves is inhibited
for the both media). In a general situation, the surface solitons form when
amplification coefficient exceeds threshold value. When a soliton is formed in
a total finite gap there exists also the upper limit for the linear gain.Comment: 5 pages, 3 figures, to appear in Europhysics Letter
Nonlinear waves of polarization in two-component Bose-Einstein condensates
Waves with different symmetries exist in two-component Bose-Einstein
condensates (BECs) whose dynamics is described by a system of coupled
Gross-Pitaevskii (GP) equations. A first type of waves corresponds to
excitations for which the motion of both components is locally in phase. In the
second type of waves the two components have a counter-phase local motion. In
the case of different values of inter- and intra-component interaction
constants, the long wave-length behavior of these two modes corresponds to two
types of sound with different velocities. In the limit of weak nonlinearity and
small dispersion the first mode is described by the well-known Korteweg-de
Vries (KdV) equation. We show that in the same limit the second mode can be
described by the Gardner (modified KdV) equation, if the intra-component
interaction constants have close enough values. This leads to a rich
phenomenology of nonlinear excitations (solitons, kinks, algebraic solitons,
breathers) which does not exist in the KdV description.Comment: 10 pages, 5 figure
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