222 research outputs found
Interface localized modes and hybrid lattice solitons in waveguide arrays
We discuss the formation of guided modes localized at the interface separat-
ing two different periodic photonic lattices. Employing the effective discrete
model, we analyze linear and nonlinear interface modes and also predict the
existence of stable interface solitons including the hybrid
staggered/unstaggered lattice solitons with the tails belonging to spectral
gaps of different types.Comment: 11 pages, 5 figures, submitted to Opt. Let
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
Discrete surface solitons in two-dimensional anisotropic photonic lattices
We study nonlinear surface modes in two-dimensional {\em anisotropic}
periodic photonic lattices and demonstrate that, in a sharp contrast to
one-dimensional discrete surface solitons, the mode threshold power is lower at
the surface, and two-dimensional discrete solitons can be generated easier near
the lattice corners and edges. We analyze the crossover between effectively
one- and two-dimensional regimes of the surface-mediated beam localization in
the lattice.Comment: 3 pages, 4 figure
Demonstration of all-optical beam steering in modulated photonic lattices
We demonstrate experimentally all-optical beam steering in modulated photonic
lattices induced optically by three beam interference in a biased
photorefractive crystal. We identify and characterize the key physical
parameters governing the beam steering, and show that the spatial resolution
can be enhanced by the additional effect of nonlinear beam self-localization.Comment: 3 pages, 3 figure
Cost per case or total cost? The potential of prevention of hand injuries in young children – Retrospective and prospective studies
<p>Abstract</p> <p>Background</p> <p>Health-care costs for hand and forearm injuries in young children are poorly documented. We examined costs in 533 children injured years 1996–2003.</p> <p>Methods</p> <p>Health-care costs and costs for lost productivity were retrospectively calculated in children from three catchment areas in Sweden. Seven case categories corresponding to alternative prevention strategies were constructed.</p> <p>Results</p> <p>Over time, diminishing number of ward days reduced the health-care cost per case. Among children, the cost of lost productivity due to parental leave was 14 percent of total cost. Fingertip injuries had low median costs but high total costs due to their frequency. Complex injuries by machine or rifle had high costs per case, and despite a low number of cases, total cost was high. Type of injury, surgery and physiotherapy sessions were associated with variations in health-care cost. Low age and ethnic background had a significant effect on number of ward days.</p> <p>Conclusion</p> <p>The costs per hand injury for children were lower compared to adults due to both lower health-care costs and to the fact that parents had comparatively short periods of absence from work. Frequent simple fingertip injuries and rare complex injuries induce high costs for society. Such costs should be related to costs for prevention of these injuries.</p
Observation of surface gap solitons in semi-infinite waveguide arrays
We report on the first observation of surface gap solitons, recently
predicted to exist at the interface between uniform and periodic dielectric
media with defocusing nonlinearity [Ya.V. Kartashov et al., Phys. Rev. Lett.
96, 073901 (2006). We demonstrate strong self-trapping at the edge of a LiNbO_3
waveguide array and the formation of staggered surface solitons with
propagation constant inside the first photonic band gap. We study the crossover
between linear repulsion and nonlinear attraction at the surface, revealing the
mechanism of nonlinearity-mediated stabilization of the surface gap modes.Comment: 4 pages, 5 figure
Observation of localized modes at phase slips in two-dimensional photonic lattices
We study experimentally light localization at phase-slip waveguides and at
the intersection of phase-slips in a two-dimensional (2D) square photonic
lattice. Such system allows to observe a variety of effects, including the
existence of spatially localized modes for low powers, the generation of
strongly localized states in the form of discrete bulk and surface solitons, as
well as a crossover between one-dimensional (1D) and 2D localization.Comment: 4 double-column pages, 6 figures, submitted for publicatio
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
Observation of two-dimensional lattice interface solitons
We report on the experimental observation of two-dimensional solitons at the
interface between square and hexagonal waveguide arrays. In addition to the
different symmetry of the lattices, the influence of a varying refractive index
modulation depth is investigated. Such variation strongly affects the
properties of surface solitons residing at different sides of the interface.Comment: 14 pages, 5 figures, to appear in Optics Letter
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