PubMed Health⌕ Search

Biomedical subjects

M Segev

Publications and source records attributed to M Segev.

At least 19 recordsLinked to original sources
PubMed2006

Incoherent white-light solitons in nonlinear periodic lattices.

We predict the existence of lattice solitons made of incoherent white light: lattice solitons made of light originating from an ordinary incandescent light bulb. We find that the intensity structure and spatial power spectra associated with different temporal frequency constituents of incoherent white-light lattice solitons (IWLLSs) arrange themselves in a characteristic fashion, with the intensity structure more localized at higher frequencies, and the spatial power spectrum more localized at lower frequencies; the spatial correlation distance is larger at lower frequency constituents of IWLLSs. This characteristic shape of incoherent white-light lattice solitons reflects the fact that diffraction is stronger for lower temporal frequency constituents, while higher frequencies experience stronger effective nonlinearity and deeper lattice structure.

Journal Article↗
PubMed2005

Incoherent matter-wave solitons and pairing instability in an attractively interacting Bose-Einstein condensate.

The dynamics of matter-wave solitons in Bose-Einstein condensates (BEC) is considerably affected by the presence of a thermal cloud and the dynamical depletion of the condensate. Our numerical results, based on the time-dependent Hartree-Fock-Bogoliubov theory, demonstrate the collapse of the attractively interacting BEC via collisional emission of atom pairs into the thermal cloud, which splits the (quasi-one-dimensional) BEC soliton into two partially coherent solitonic structures of opposite momenta. These incoherent matter waves are analogous to optical random-phase solitons.

Journal Article↗
PubMed2004

Random-phase solitons in nonlinear periodic lattices.

We predict the existence of random phase solitons in nonlinear periodic lattices. These solitons exist when the nonlinear response time is much longer than the characteristic time of random phase fluctuations. The intensity profiles, power spectra, and statistical (coherence) properties of these stationary waves conform to the periodicity of the lattice. The general phenomenon of such solitons is analyzed in the context of nonlinear photonic lattices.

Journal Article↗
PubMed2003

Incoherent white light solitons in logarithmically saturable noninstantaneous nonlinear media.

We analytically demonstrate the existence of white light solitons in logarithmically saturable noninstantaneous nonlinear media. This incoherent soliton has elliptic Gaussian intensity profile, and elliptic Gaussian spatial correlation statistics. The existence curve of the soliton connects the strength of the nonlinearity, the spatial correlation distance as a function of frequency, and the characteristic width of the soliton. For this soliton to exist, the spatial correlation distance must be smaller for larger temporal frequency constituents of the beam.

Journal Article↗
PubMed2001

Mathematical frontiers in optical solitons.

Solitons are localized concentrations of field energy, resulting from a balance of dispersive and nonlinear effects. They are ubiquitous in the natural sciences. In recent years optical solitons have arisen in new and exciting contexts that differ in many ways from the original context of coherent propagation in a uniform medium. We review recent developments in incoherent spatial solitons and in gap solitons in periodic structures.

Journal Article↗
PubMed2001

Rotating propeller solitons.

We demonstrate experimentally and theoretically (both analytically and numerically) a new type of spatial soliton: a rotating "propeller" soliton. This is a composite soliton made of a rotating dipole component jointly trapped with a bell-shaped component. We observe as much as 239 degrees of rotation over 13 mm of propagation (6.5 diffraction lengths).

Journal Article↗
PubMed2001

Interactions between two-dimensional composite vector solitons carrying topological charges.

We present a comprehensive study of interactions (collisions) between two-dimensional composite vector solitons carrying topological charges in isotropic saturable nonlinear media. We numerically study interactions between such composite solitons for different regimes of collision angle and report numerous effects which are caused solely by the "spin" (topological charge) carried by the second excited mode. The most intriguing phenomenon we find is the delayed-action interaction between interacting composite solitons carrying opposite spins. In this case, two colliding solitons undergo a fusion process and form a metastable bound state that decays after long propagation distances into two or three new solitons. Another noticeable effect is spin-orbit coupling in which angular momentum is being transferred from "spin" to orbital angular momentum. This phenomenon occurs at angles below the critical angle, including the case when the initial soliton trajectories are in parallel to one another and lie in the same plane. Finally, we report on shape transformation of vortex component into a rotating dipole-mode solitons that occurs at large collision angles, i.e., at angles for which scalar solitons of all types simply go through one another unaffected.

Journal Article↗
PubMed2000

Eliminating the transverse instabilities of kerr solitons

We show analytically, numerically, and experimentally that a transversely stable one-dimensional [(1+1)D] bright Kerr soliton can exist in a 3D bulk medium. The transverse instability of the soliton is completely eliminated if it is made sufficiently incoherent along the transverse dimension. We derive a criterion for the threshold of transverse instability that links the nonlinearity to the largest transverse correlation distance for which the 1D soliton is stable.

Journal Article↗
PubMed2000

Modulation instability and pattern formation in spatially incoherent light beams.

We report on the experimental observation of modulation instability of partially spatially incoherent light beams in noninstantaneous nonlinear media and show that in such systems patterns can form spontaneously from noise. Incoherent modulation instability occurs above a specific threshold that depends on the coherence properties (correlation distance) of the wave packet and leads to a periodic train of one-dimensional filaments. At a higher value of nonlinearity, the incoherent one-dimensional filaments display a two-dimensional instability and break up into self-ordered arrays of light spots. This discovery of incoherent pattern formation reflects on many other nonlinear systems beyond optics. It implies that patterns can form spontaneously (from noise) in diverse nonlinear many-body systems involving weakly correlated particles, such as atomic gases at (or near) Bose-Einstein condensation temperatures and electrons in semiconductors at the vicinity of the quantum Hall regime.

Journal Article↗
PubMed2000

Bright spatial solitons on a partially incoherent background

We present the first observation of incoherent antidark spatial solitons in noninstantaneous nonlinear media. This new class of soliton states involves bright solitons on a partially incoherent background of infinite extent. In the case where the nonlinearity is of the Kerr type, their existence is demonstrated analytically by means of an exact solution. Computer simulations and experiments indicate that these incoherent antidark solitons can propagate in a stable fashion provided that the spatial coherence of their background is reduced below the incoherent modulation instability threshold.

Journal Article↗
PubMed2000

Cantor set fractals from solitons

We show how a nonlinear system that supports solitons can be driven to generate exact (regular) Cantor set fractals. As an example, we use numerical simulations to demonstrate the formation of Cantor set fractals by temporal optical solitons. This fractal formation occurs in a cascade of nonlinear optical fibers through the dynamical evolution from a single input soliton.

Journal Article↗
PubMed2000

Composite multihump vector solitons carrying topological charge

We propose composite solitons carrying topological charge: multicomponent two dimensional [ (2+1)D] vector (Manakov-like) solitons for which at least one component carries topological charge. These multimode solitons can have a single hump or exhibit a multihump structure. The "spin" carried by these multimode composite solitons suggests 3D soliton interactions in which the particlelike behavior includes spin, in addition to effective mass, linear, and angular momenta.

Journal Article↗
PubMed2000

Self-similarity and fractals in soliton-supporting systems

We describe a principle that can be used to generate self-similarity and fractals in almost any nonlinear system in nature that supports solitons, given that some proper nonadiabatic conditions are met. We illustrate our idea on a particular optics example that also theoretically demonstrates fractals in nonlinear optics.

Journal Article↗
PubMed2000

Self-trapping of "necklace-ring" beams in self-focusing kerr media

Recently, we suggested a type of self-trapped optical beams that can propagate in a stable form in (2+1)D self-focusing Kerr media: Necklace-ring beams [M. Soljacic, S. Sears, and M. Segev, Phys. Rev. Lett. 81, 4851 (1998)]. These self-trapped necklaces slowly expand their ring diameter as they propagate as a result of a net radial force that adjacent "pearls" (azimuthal spots) exert on each other. Here, we revisit the self-trapped necklace beams and investigate their properties analytically and numerically. Specifically, we use two different approaches and find analytic expressions for the propagation dynamics of the necklace beams. We show that the expansion dynamics can be controlled and stopped for more than 40 diffraction lengths, making it possible to start thinking about interaction-collision phenomena between self-trapped necklaces and related soliton effects. Such self-trapped necklace-ring beams should also be observable in all other nonlinear systems described by the cubic (2+1)D nonlinear Shrodinger equation-in almost all nonlinear systems in nature that describe envelope waves.

Journal Article↗