962 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
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
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
Neutrino Spin Transitions and the Violation of the Equivalence Principle
The violation of the equivalence principle (VEP) causing neutrino
oscillations is of current interest. We study here the possibility of not only
flavor oscillation but spin flavor oscillation of ultra high energy ( 1
PeV) neutrinos emanating from AGN due to VEP and due to the presence of a large
magnetic field ( 1 Tesla) in AGN. In particular we look at the resonance
spin flavor conversion driven by the AGN potential. Interesting bounds on the
transition magnetic moment of neutrinos may therefore be obtained.Comment: Latex, 12 pages, no figures. To appear in Journal of Physics G:
Nuclear and Particle Physics. Two references adde
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
Spatiotemporally Localized Multidimensional Solitons in Self-Induced Transparency Media
"Light bullets" are multi-dimensional solitons which are localized in both
space and time. We show that such solitons exist in two- and three-dimensional
self-induced-transparency media and that they are fully stable. Our approximate
analytical calculation, backed and verified by direct numerical simulations,
yields the multi-dimensional generalization of the one-dimensional Sine-Gordon
soliton.Comment: 4 pages, 4 figures, to appear in Phys. Rev. Let
Switching of Discrete Solitons in Engineered Waveguide Arrays
We demonstrate a simple method for controlling nonlinear switching of
discrete solitons in arrays of weakly coupled optical waveguides, for both
cubic and uadratic nonlinearities. Based on the effective discrete nonlinear
equations describing the waveguide arrays in the tight-binding approximation,
we develop the concept of the array engineering by means of a step-like
variation of the waveguide coupling. We demonstrate the digitized switching of
a narrow input beam for up to eleven neighboring waveguides, in the case of the
cubic nonlinearity, and up to ten waveguides, in the case of quadratic
nonlinearity. We discuss our predictions in terms of the physics of the
engineered Peierls-Nabarro (PN) potential experienced by strongly localized
nonlinear modes moving in a lattice and calculate, for the first time, the PN
potential for the quadratic nonlinear array. We also confirm our concept and
major findings for a full-scaled continuous model and realistic parameters, by
means of the beam propagation method.Comment: 9 pages, 8 figures, to be submitted to Physical review
On the Properties of Two Pulses Propagating Simultaneously in Different Dispersion Regimes in a Nonlinear Planar Waveguide
Properties of two pulses propagating simultaneously in different dispersion
regimes, anomalous and normal, in a Kerr-type planar waveguide are studied in
the framework of the nonlinear Schroedinger equation. Catastrophic
self-focusing and spatio-temporal splitting of the pulses is investigated. For
the limiting case when the dispersive term of the pulse propagating in the
normal dispersion regime can be neglected an indication of a possibility of a
stable self-trapped propagation of both pulses is obtained.Comment: 18 pages (including 15 eps figures
Systematics of the release of residual nuclei from relativistic nucleus-nucleus interactions
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