116 research outputs found
Spatiotemporal solitons in dispersion-managed multimode fibers
We develop the scheme of dispersion management (DM) for three-dimensional
(3D) solitons in a multimode optical fiber. It is modeled by the parabolic
confining potential acting in the transverse plane in combination with the
cubic self-focusing. The DM map is adopted in the form of alternating segments
with anomalous and normal group-velocity dispersion. Previously, temporal DM
solitons were studied in detail in single-mode fibers, and some solutions for
2D spatiotemporal "light bullets", stabilized by DM, were found in the model of
a planar waveguide. By means of numerical methods, we demonstrate that
stability of the 3D spatiotemporal solitons is determined by the usual
DM-strength parameter, : they are quasi-stable at ,
and completely stable at . Stable vortex solitons are constructed too.
We also consider collisions between the 3D solitons, in both axial and
transverse directions. The interactions are quasi-elastic, including periodic
collisions between solitons which perform shuttle motion in the transverse
plane.Comment: 15 pages, 13 figures, to be published in Journal of Optic
Spatiotemporal solitons in dispersion-managed multimode fibers
We develop the scheme of dispersion management (DM) for three-dimensional (3D) solitons in a multimode optical fiber. It is modeled by the parabolic confining potential acting in the transverse plane in combination with the cubic self-focusing. The DM map is adopted in the form of alternating segments with anomalous and normal group-velocity dispersion. Previously, temporal DM solitons were studied in detail in single-mode fibers, and some solutions for 2D spatiotemporal 'light bullets', stabilized by DM, were found in the model of a planar waveguide. By means of numerical methods, we demonstrate that stability of the 3D spatiotemporal solitons is determined by the usual DM-strength parameter, S: they are quasi-stable at , and completely stable at . Stable vortex solitons are constructed too. We also consider collisions between the 3D solitons, in both axial and transverse directions. The interactions are quasi-elastic, including periodic collisions between solitons which perform shuttle motion in the transverse plane
Gap solitons in a model of a hollow optical fiber
We introduce a models for two coupled waves propagating in a hollow-core
fiber: a linear dispersionless core mode, and a dispersive nonlinear
quasi-surface one. The linear coupling between them may open a bandgap, through
the mechanism of the avoidance of crossing between dispersion curves. The
third-order dispersion of the quasi-surface mode is necessary for the existence
of the gap. Numerical investigation reveals that the entire bandgap is filled
with solitons, and they all are stable in direct simulations. The gap-soliton
(GS) family is extended to include pulses moving relative to the given
reference frame, up to limit values of the corresponding boost ,
beyond which the solitons do not exists. The limit values are nonsymmetric for
and . The extended gap is also entirely filled with the
GSs, all of which are stable in simulations. Recently observed solitons in
hollow-core photonic-crystal fibers may belong to this GS family.Comment: 5 pages, 5 figure
Can ID Repetitive Elements Serve as Cis-acting Dendritic Targeting Elements? An In Vivo Study
Dendritic localization of mRNA/RNA involves interaction of cis-elements and trans-factors. Small, non-protein coding dendritic BC1 RNA is thought to regulate translation in dendritic microdomains. Following microinjections into cultured cells, BC1 RNA fused to larger mRNAs appeared to impart transport competence to these chimeras, and its 5′ ID region was proposed as the cis-acting dendritic targeting element. As these ID elements move around rodent genomes and, if transcribed, form a long RNA stem-loop, they might, thereby, lead to new localizations for targeted gene products. To test their targeting ability in vivo we created transgenic mice expressing various ID elements fused to the 3′ UTR of reporter mRNA for Enhanced Green Fluorescent Protein. In vivo, neither ID elements nor the BC1 RNA coding region were capable of transporting EGFP RNA to dendrites, although the 3′ UTR of α-CaMKII mRNA, an established cis-acting element did produce positive results. Other mRNAs containing naturally inserted ID elements are also not found in neuronal dendrites. We conclude that the 5′ ID domain from BC1 RNA is not a sufficient dendritic targeting element for mRNAs in vivo
Light Bullet Modes in Self-Induced-Transparency Media with Refractive Index Modulation
We predict the existence of a new type of spatiotemporal solitons ("light
bullets") in two-dimensional self-induced-transparency media with refractive
index modulation in the direction transverse to that of pulse propagation.
These self-localized guided modes are found in an approximate analytical form,
their existence and stability being confirmed by numerical simulations, and may
have advantageous properties for signal transmission
Stability of spinning ring solitons of the cubic-quintic nonlinear Schrodinger equation
We investigate stability of (2+1)-dimensional ring solitons of the nonlinear
Schrodinger equation with focusing cubic and defocusing quintic nonlinearities.
Computing eigenvalues of the linearised equation, we show that rings with spin
(topological charge) s=1 and s=2 are linearly stable, provided that they are
very broad. The stability regions occupy, respectively, 9% and 8% of the
corresponding existence regions. These results finally resolve a controversial
stability issue for this class of models.Comment: 10 pages, 5 figures, accepted to Phys. Lett.
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