5,803 research outputs found

### Limits to compression with cascaded quadratic soliton compressors

We study cascaded quadratic soliton compressors and address the physical
mechanisms that limit the compression. A nonlocal model is derived, and the
nonlocal response is shown to have an additional oscillatory component in the
nonstationary regime when the group-velocity mismatch (GVM) is strong. This
inhibits efficient compression. Raman-like perturbations from the cascaded
nonlinearity, competing cubic nonlinearities, higher-order dispersion, and
soliton energy may also limit compression, and through realistic numerical
simulations we point out when each factor becomes important. We find that it is
theoretically possible to reach the single-cycle regime by compressing
high-energy fs pulses for wavelengths $\lambda=1.0-1.3 \mu{\rm m}$ in a
$\beta$-barium-borate crystal, and it requires that the system is in the
stationary regime, where the phase mismatch is large enough to overcome the
detrimental GVM effects. However, the simulations show that reaching
single-cycle duration is ultimately inhibited by competing cubic nonlinearities
as well as dispersive waves, that only show up when taking higher-order
dispersion into account.Comment: 16 pages, 5 figures, submitted to Optics Expres

### Measuring the mass of a sterile neutrino with a very short baseline reactor experiment

An analysis of the world's neutrino oscillation data, including sterile
neutrinos, (M. Sorel, C. M. Conrad, and M. H. Shaevitz, Phys. Rev. D 70,
073004) found a peak in the allowed region at a mass-squared difference $\Delta
m^2 \cong 0.9$ eV$^2$. We trace its origin to harmonic oscillations in the
electron survival probability $P_{ee}$ as a function of L/E, the ratio of
baseline to neutrino energy, as measured in the near detector of the Bugey
experiment. We find a second occurrence for $\Delta m^2 \cong 1.9$ eV$^2$. We
point out that the phenomenon of harmonic oscillations of $P_{ee}$ as a
function of L/E, as seen in the Bugey experiment, can be used to measure the
mass-squared difference associated with a sterile neutrino in the range from a
fraction of an eV$^2$ to several eV$^2$ (compatible with that indicated by the
LSND experiment), as well as measure the amount of electron-sterile neutrino
mixing. We observe that the experiment is independent, to lowest order, of the
size of the reactor and suggest the possibility of a small reactor with a
detector sitting at a very short baseline.Comment: 4 pages, 2 figure

### Optical vault: reconfigurable bottle beam by conically refracted light

We employ conical refraction of light in a biaxial crystal to create an
optical bottle for trapping and manipulation of particles. We show that by just
varying the polarization of the input light the bottle can be opened and closed
at will. We experimentally demonstrate stable photophoretic trapping and
controllable loading and unloading of light absorbing particles in the trap.Comment: 4 pages, 5 figure

### Collapse in the nonlocal nonlinear Schr\"odinger equation

We discuss spatial dynamics and collapse scenarios of localized waves
governed by the nonlinear Schr\"{o}dinger equation with nonlocal nonlinearity.
Firstly, we prove that for arbitrary nonsingular attractive nonlocal nonlinear
interaction in arbitrary dimension collapse does not occur. Then we study in
detail the effect of singular nonlocal kernels in arbitrary dimension using
both, Lyapunoff's method and virial identities. We find that for for a
one-dimensional case, i.e. for $n=1$, collapse cannot happen for nonlocal
nonlinearity. On the other hand, for spatial dimension $n\geq2$ and singular
kernel $\sim 1/r^\alpha$, no collapse takes place if $\alpha<2$, whereas
collapse is possible if $\alpha\ge2$. Self-similar solutions allow us to find
an expression for the critical distance (or time) at which collapse should
occur in the particular case of $\sim 1/r^2$ kernels. Moreover, different
evolution scenarios for the three dimensional physically relevant case of Bose
Einstein condensate are studied numerically for both, the ground state and a
higher order toroidal state with and without an additional local repulsive
nonlinear interaction. In particular, we show that presence of an additional
local repulsive term can prevent collapse in those cases

### Generation of the second-harmonic Bessel beams via nonlinear Bragg diffraction

We generate conical second-harmonic radiation by transverse excitation of a
two-dimensional annular periodically-poled nonlinear photonic structure with a
fundamental Gaussian beam. We show that these conical waves are the far-field
images of the Bessel beams generated in a crystal by parametric frequency
conversion assisted by nonlinear Bragg diffraction.Comment: 4 pages, 5 figures. submitte

### Local demands on sterile neutrinos

In a model independent manner, we explore the local implications of a single
neutrino oscillation measurement which cannot be reconciled within a
three-neutrino theory. We examine this inconsistency for a single region of
baseline to neutrino energy $L/E$. Assuming that sterile neutrinos account for
the anomaly, we find that the {\it local} demands of this datum can require the
addition to the theory of one to three sterile neutrinos. We examine the
constraints which can be used to determine when more than one neutrino would be
required. The results apply only to a given region of $L/E$. The question of
the adequacy of the sterile neutrinos to satisfy a global analysis is not
addressed here. Finally, using the results of a 3+2 analysis, we indicate
values for unknown mixing matrix elements which would require two sterile
neutrinos due to local demands only.Comment: 11 pages, 1 figure, discussion adde

### Anisotropic charge displacement supporting isolated photorefractive optical needles

The strong asymmetry in charge distribution supporting a single
non-interacting spatial needle soliton in a paraelectric photorefractive is
directly observed by means of electroholographic readout. Whereas in trapping
conditions a quasi-circular wave is supported, the underlying double-dipolar
structure can be made to support two distinct propagation modes.Comment: 3 pages, 3 figure

### Nonlinear Bloch-wave interaction and Bragg scattering in optically-induced lattices

We study, both theoretically and experimentally, the Bragg scattering of
light in optically-induced photonic lattices and reveal the key physical
mechanisms which govern nonlinear self-action of narrow beams under the
combined effects of Bragg scattering and wave diffraction, allowing for
selecting bands with different effective dispersion.Comment: 4 pages, 6 figure

### Helmholtz bright and boundary solitons

We report, for the first time, exact analytical boundary solitons of a generalized cubic-quintic Non-Linear Helmholtz (NLH) equation. These solutions have a linked-plateau topology that is distinct from conventional dark soliton solutions; their amplitude and intensity distributions are spatially delocalized and connect regions of finite and zero wave-field disturbances (suggesting also the classification as 'edge solitons'). Extensive numerical simulations compare the stability properties of recently-reported Helmholtz bright solitons, for this type of polynomial non-linearity, to those of the new boundary solitons. The latter are found to possess a remarkable stability characteristic, exhibiting robustness against perturbations that would otherwise lead to the destabilizing of their bright-soliton counterpart

### Reduced-symmetry two-dimensional solitons in photonic lattices

We demonstrate theoretically and experimentally a novel type of localized
beams supported by the combined effects of total internal and Bragg reflection
in nonlinear two-dimensional square periodic structures. Such localized states
exhibit strong anisotropy in their mobility properties, being highly mobile in
one direction and trapped in the other, making them promising candidates for
optical routing in nonlinear lattices.Comment: 5 pages, 4 figure

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