825 research outputs found
Nonlinear Band Gap Transmission in Optical Waveguide Arrays
The effect of nonlinear transmission in coupled optical waveguide arrays is
theoretically investigated via numerical simulations on the corresponding model
equations. The realistic experimental setup is suggested injecting the beam in
a single boundary waveguide, linear refractive index of which () is larger
than one () of other identical waveguides in the array. Particularly, the
effect holds if , where is a linear coupling constant
between array waveguides, is a carrier wave frequency and is a
light velocity. Making numerical experiments in case of discrete nonlinear
Schr\"odinger equation it is shown that the energy transfers from the boundary
waveguide to the waveguide array above certain threshold intensity of the
injected beam. This effect is explained by means of the creation and
propagation of gap solitons in full analogy with the similar phenomenon of
nonlinear supratransmission [F. Geniet, J. Leon, PRL, {\bf 89}, 134102, (2002)]
in case of discrete sine-Gordon lattice.Comment: 4 pages, 6 figures. Phys. Rev. Lett. (in press
Direct access to quantum fluctuations through cross-correlation measurements
Detection of the quantum fluctuations by conventional methods meets certain
obstacles, since it requires high frequency measurements. Moreover, quantum
fluctuations are normally dominated by classical noise, and are usually further
obstructed by various accompanying effects such as a detector backaction. In
present work, we demonstrate that these difficulties can be bypassed by
performing the cross-correlation measurements. We propose to use a pair of
two-level detectors, weakly coupled to a collective mode of an electric
circuit. Fluctuations of the current source accumulated in the collective mode
induce stochastic transitions in the detectors. These transitions are then read
off by quantum point contact (QPC) electrometers and translated into two
telegraph processes in the QPC currents. Since both detectors interact with the
same collective mode, this leads to a certain fraction of the correlated
transitions. These correlated transitions are fingerprinted in the
cross-correlations of the telegraph processes, which can be detected at zero
frequency, i.e., with a long time measurements. Concerning the dependance of
the cross-correlator on the detectors' energy splittings, the most interesting
region is at the degeneracy points, where it exhibits a sharp non-local
resonance, that stems from higher order processes. We find that at certain
conditions the main contribution to this resonance comes from the quantum
noise. Namely, while the resonance line shape is weakly broadened by the
classical noise, the height of the peak is directly proportional to the square
of the quantum component of the noise spectral function.Comment: Added discussion of the time scales in the introduction and one
figure. 14 pages, 8 figure
Multiparticle Interference, GHZ Entanglement, and Full Counting Statistics
We investigate the quantum transport in a generalized N-particle Hanbury
Brown--Twiss setup enclosing magnetic flux, and demonstrate that the Nth-order
cumulant of current cross correlations exhibits Aharonov-Bohm oscillations,
while there is no such oscillation in all the lower-order cumulants. The
multiparticle interference results from the orbital Greenberger-Horne-Zeilinger
entanglement of N indistinguishable particles. For sufficiently strong
Aharonov-Bohm oscillations the generalized Bell inequalities may be violated,
proving the N-particle quantum nonlocality.Comment: 4 pages, 1 figure, published versio
Transport Statistics of Bistable Systems
We consider the transport statistics of classical bistable systems driven by
noise. The stochastic path integral formalism is used to investigate the
dynamics and distribution of transmitted charge. Switching rates between the
two stable states are found from an instanton calculation, leading to an
effective two-state system on a long time scale. In the bistable current range,
the telegraph noise dominates the distribution, whose logarithm is found to be
universally described by a tilted ellipse.Comment: 4 pages, 3 figures, version to appear in Phys. Rev. Let
Spatial optical solitons supported by mutual focusing
We study composite spatial optical solitons supported by two-wave mutual
focusing induced by cross-phase modulation in Kerr-like nonlinear media. We
find the families of both single- and two-hump solitons and discuss their
properties and stability. We also reveal remarkable similarities between
recently predicted holographic solitons in photorefractive media and parametric
solitons in quadratic nonlinear crystals.Comment: 3 pages, 3 figure
Discrete interband mutual focusing in nonlinear photonic lattices
We study nonlinear coupling of mutually incoherent beams associated with
different Floquet-Bloch waves in a one-dimensional optically-induced photonic
lattice. We demonstrate experimentally how such interactions lead to asymmetric
mutual focusing and, for waves with opposite diffraction properties, to
simultaneous focusing and defocusing as well as discreteness-induced beam
localization and reshaping effects.Comment: 8 pages, 6 figures. To download the associated .avi movie, go to
http://www.rsphysse.anu.edu.au/~crr124/mut_focus
Plasmonic Bloch oscillations in chirped metal-dielectric structures
We study the propagation of plasmon polaritons in one-dimensional chirped metal-dielectric layered structures. We find an optical Wannier–Stark ladder in the mode spectrum and analyze Bloch oscillations associated with the coupling of surface plasmons localized at the metal-dielectric interfaces. For long structures, we find that the energy flow may dramatically change its direction, thus providing possibilities for the beam steering in the transmission band.The work has been supported by the Australian Research
Council
Crossover from self-defocusing to discrete trapping in nonlinear waveguide arrays
We predict a sharp crossover from nonlinear self-defocusing to discrete
self-trapping of a narrow Gaussian beam with the increase of the refractive
index contrast in a periodic photonic lattice. We demonstrate experimentally
nonlinear discrete localization of light with defocusing nonlinearity by single
site excitation in LiNbO waveguide arrays.Comment: 6 pages, 4 figure
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