648 research outputs found
Soliton dynamics in the multiphoton plasma regime
Solitary waves have consistently captured the imagination of scientists,
ranging from fundamental breakthroughs in spectroscopy and metrology enabled by
supercontinuum light, to gap solitons for dispersionless slow-light, and
discrete spatial solitons in lattices, amongst others. Recent progress in
strong-field atomic physics include impressive demonstrations of attosecond
pulses and high-harmonic generation via photoionization of free-electrons in
gases at extreme intensities of 1014 Wcm2. Here we report the first
phase-resolved observations of femtosecond optical solitons in a semiconductor
microchip, with multiphoton ionization at picojoule energies and 1010 Wcm2
intensities. The dramatic nonlinearity leads to picojoule observations of
free-electron-induced blue-shift at 1016 cm3 carrier densities and self-chirped
femtosecond soliton acceleration. Furthermore, we evidence the time-gated
dynamics of soliton splitting on-chip, and the suppression of soliton
recurrence due to fast free-electron dynamics. These observations in the highly
dispersive slow-light media reveal a rich set of physics governing
ultralow-power nonlinear photon-plasma dynamics.Comment: 14 pages (main body and supplement), 11 figures - earlier draft;
http://www.nature.com/srep/2013/130122/srep01100/full/srep01100.htm
Helmholtz bright spatial solitons and surface waves at power-law optical interfaces
We consider arbitrary-angle interactions between spatial solitons and the planar boundary between two optical materials with a single power-law nonlinear refractive index. Extensive analysis has uncovered a wide range of new qualitative phenomena in non-Kerr regimes. A universal Helmholtz-Snell law describing soliton refraction is derived using exact solutions to the governing equation as a nonlinear basis. New predictions are tested through exhaustive computations, which have uncovered substantially enhanced Goos-Hänchen shifts at some non-Kerr interfaces. Helmholtz nonlinear surface waves are analyzed theoretically, and their stability properties are investigated numerically for the first time. Interactions between surface waves and obliquely-incident solitons are also considered. Novel solution behaviours have been uncovered, which depend upon a complex interplay between incidence angle, medium mismatch parameters, and the power-law nonlinearity exponent
Transverse Patterns in Nonlinear Optical Resonators
The book is devoted to the formation and dynamics of localized structures
(vortices, solitons) and extended patterns (stripes, hexagons, tilted waves) in
nonlinear optical resonators such as lasers, optical parametric oscillators,
and photorefractive oscillators. The theoretical analysis is performed by
deriving order parameter equations, and also through numerical integration of
microscopic models of the systems under investigation. Experimental
observations, and possible technological implementations of transverse optical
patterns are also discussed. A comparison with patterns found in other
nonlinear systems, i.e. chemical, biological, and hydrodynamical systems, is
given. This article contains the table of contents and the introductory chapter
of the book.Comment: 37 pages, 14 figures. Table of contents and introductory chapter of
the boo
Slowdown and splitting of gap solitons in apodized Bragg gratings
We study the motion of gap solitons in two models of apodized nonlinear fiber
Bragg gratings (BGs), with the local reflectivity (LR) varying along the fiber.
A single step of LR, and a periodic array of alternating steps with opposite
signs (a "Bragg superstructure") are considered. A challenging possibility is
to slow down and eventually halt the soliton by passing it through the step of
increasing reflectivity, thus capturing a pulse of standing light. First, we
develop an analytical approach, assuming adiabatic evolution of the soliton,
and making use of the energy conservation and balance equation for the
momentum. Comparison with simulations shows that the analytical approximation
is quite accurate (unless the inhomogeneity is too steep): the soliton is
either transmitted across the step or bounces back. If the step is narrow,
systematic simulations demontrate that the soliton splits into transmitted and
reflected pulses (splitting of a BG soliton which hits a chirped grating was
observed in experiments). Moving through the periodic "superstructure", the
soliton accummulates distortion and suffers radiation loss if the structure is
composed of narrow steps. The soliton moves without any loss or irreversible
deformation through the array of sufficiently broad steps.Comment: to appear in a special issue on Wave-Optical Engineering, Journal of
Modern Optic
Dynamics of ring dark solitons in Bose-Einstein condensates and nonlinear optics
Quasiparticle approach to dynamics of dark solitons is applied to the case of
ring solitons. It is shown that the energy conservation law provides the
effective equations of motion of ring dark solitons for general form of the
nonlinear term in the generalized nonlinear Schroedinger or Gross-Pitaevskii
equation. Analytical theory is illustrated by examples of dynamics of ring
solitons in light beams propagating through a photorefractive medium and in
non-uniform condensates confined in axially symmetric traps. Analytical results
agree very well with the results of our numerical simulations.Comment: 10 pages, 4 figure
The entropy of black holes: a primer
After recalling the definition of black holes, and reviewing their energetics
and their classical thermodynamics, one expounds the conjecture of Bekenstein,
attributing an entropy to black holes, and the calculation by Hawking of the
semi-classical radiation spectrum of a black hole, involving a thermal
(Planckian) factor. One then discusses the attempts to interpret the black-hole
entropy as the logarithm of the number of quantum micro-states of a macroscopic
black hole, with particular emphasis on results obtained within string theory.
After mentioning the (technically cleaner, but conceptually more intricate)
case of supersymmetric (BPS) black holes and the corresponding counting of the
degeneracy of Dirichlet-brane systems, one discusses in some detail the
``correspondence'' between massive string states and non-supersymmetric
Schwarzschild black holes.Comment: 51 pages, 4 figures, talk given at the "Poincare seminar" (Paris, 6
December 2003), to appear in Poincare Seminar 2003 (Birkhauser
Pump-and-probe optical transmission phase shift as a quantitative probe of the Bogoliubov dispersion relation in a nonlinear channel waveguide
We theoretically investigate the dispersion relation of small-amplitude
optical waves superimposing upon a beam of polarized monochromatic light
propagating along a single-mode channel waveguide characterized by an
instantaneous and spatially local Kerr nonlinearity. These small luminous
fluctuations propagate along the waveguide as Bogoliubov elementary excitations
on top of a one-dimensional dilute Bose quantum fluid evolve in time. They
consequently display a strongly renormalized dispersion law, of Bogoliubov
type. Analytical and numerical results are found in both the absence and the
presence of one- and two-photon losses. Silicon and silicon-nitride waveguides
are used as examples. We finally propose an experiment to measure this
Bogoliubov dispersion relation, based on a stimulated four-wave mixing and
interference spectroscopy techniques.Comment: 17 pages, 7 figure
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