1,185 research outputs found
Parametric Self-Oscillation via Resonantly Enhanced Multiwave Mixing
We demonstrate an efficient nonlinear process in which Stokes and anti-Stokes
components are generated spontaneously in a Raman-like, near resonant media
driven by low power counter-propagating fields. Oscillation of this kind does
not require optical cavity and can be viewed as a spontaneous formation of
atomic coherence grating
All-Optical Switching with Transverse Optical Patterns
We demonstrate an all-optical switch that operates at ultra-low-light levels
and exhibits several features necessary for use in optical switching networks.
An input switching beam, wavelength , with an energy density of
photons per optical cross section [] changes
the orientation of a two-spot pattern generated via parametric instability in
warm rubidium vapor. The instability is induced with less than 1 mW of total
pump power and generates several Ws of output light. The switch is
cascadable: the device output is capable of driving multiple inputs, and
exhibits transistor-like signal-level restoration with both saturated and
intermediate response regimes. Additionally, the system requires an input power
proportional to the inverse of the response time, which suggests thermal
dissipation does not necessarily limit the practicality of optical logic
devices
Anisotropic solitons in dipolar Bose-Einstein Condensates
Starting with a Gaussian variational ansatz, we predict anisotropic bright
solitons in quasi-2D Bose-Einstein condensates consisting of atoms with dipole
moments polarized \emph{perpendicular} to the confinement direction. Unlike
isotropic solitons predicted for the moments aligned with the confinement axis
[Phys. Rev. Lett. \textbf{95}, 200404 (2005)], no sign reversal of the
dipole-dipole interaction is necessary to support the solitons. Direct 3D
simulations confirm their stability.Comment: 5 pages, 4 figure
Slow-light optical bullets in arrays of nonlinear Bragg-grating waveguides
We demonstrate how to control independently both spatial and temporal
dynamics of slow light. We reveal that specially designed nonlinear waveguide
arrays with phase-shifted Bragg gratings demonstrate the frequency-independent
spatial diffraction near the edge of the photonic bandgap, where the group
velocity of light can be strongly reduced. We show in numerical simulations
that such structures allow a great flexibility in designing and controlling
dispersion characteristics, and open a way for efficient spatiotemporal
self-trapping and the formation of slow-light optical bullets.Comment: 4 pages, 4 figures; available from
http://link.aps.org/abstract/PRL/v97/e23390
Azimuthally polarized spatial dark solitons: exact solutions of Maxwell's equations in a Kerr medium
Spatial Kerr solitons, typically associated with the standard paraxial
nonlinear Schroedinger equation, are shown to exist to all nonparaxial orders,
as exact solutions of Maxwell's equations in the presence of vectorial Kerr
effect. More precisely, we prove the existence of azimuthally polarized,
spatial, dark soliton solutions of Maxwell's equations, while exact linearly
polarized (2+1)-D solitons do not exist. Our ab initio approach predicts the
existence of dark solitons up to an upper value of the maximum field amplitude,
corresponding to a minimum soliton width of about one fourth of the wavelength.Comment: 4 pages, 4 figure
Self-trapped bidirectional waveguides in a saturable photorefractive medium
We introduce a time-dependent model for the generation of joint solitary
waveguides by counter-propagating light beams in a photorefractive crystal.
Depending on initial conditions, beams form stable steady-state structures or
display periodic and irregular temporal dynamics. The steady-state solutions
are non-uniform in the direction of propagation and represent a general class
of self-trapped waveguides, including counterpropagating spatial vector
solitons as a particular case.Comment: 4 pages, 5 figure
Transform-limited pulses are not optimal for resonant multiphoton transitions
Maximizing nonlinear light-matter interactions is a primary motive for
compressing laser pulses to achieve ultrashort transform limited pulses. Here
we show how, by appropriately shaping the pulses, resonant multiphoton
transitions can be enhanced significantly beyond the level achieved by
maximizing the pulse's peak intensity. We demonstrate the counterintuitive
nature of this effect with an experiment in a resonant two-photon absorption,
in which, by selectively removing certain spectral bands, the peak intensity of
the pulse is reduced by a factor of 40, yet the absorption rate is doubled.
Furthermore, by suitably designing the spectral phase of the pulse, we increase
the absorption rate by a factor of 7.Comment: 4 pages, 3 figure
Outside- in single-lasso loop technique for meniscal repair: Fast, economic, and reproducible
The current understanding of the biomechanical role of the meniscus, in conjunction with the increasing efforts to achieve its preservation within the orthopaedic community during treatment of meniscal lesions, has prompted the development of different meniscal repair techniques. The outside-in technique is recommended for anterior horn and middle-segment meniscal tears and has been recognized as a low-cost procedure with a low incidence of complications. Diverse modifications of this technique have been published over the past decade. On the basis of these previous outside-in technique modifications and aiming to simplify and reduce the number of surgical steps, as well as simplify suture and/or instrument manipulation, during this technique, we describe the single–lasso loop outside-in technique for meniscal repair. We believe this modified technique represents a simplified, economic, and highly reproducible procedure option whenever an outside-in technique for meniscal repair is considered
Quantum walks of correlated particles
Quantum walks of correlated particles offer the possibility to study
large-scale quantum interference, simulate biological, chemical and physical
systems, and a route to universal quantum computation. Here we demonstrate
quantum walks of two identical photons in an array of 21 continuously
evanescently-coupled waveguides in a SiOxNy chip. We observe quantum
correlations, violating a classical limit by 76 standard deviations, and find
that they depend critically on the input state of the quantum walk. These
results open the way to a powerful approach to quantum walks using correlated
particles to encode information in an exponentially larger state space
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