Two-color discrete localized modes and resonant scattering in arrays of nonlinear quadratic optical waveguides

We analyze the properties and stability of two-color discrete localized modes in arrays of channel waveguides where tunable quadratic nonlinearity is introduced as a nonlinear defect by periodic poling of a single waveguide in the array. We show that, depending on the value of the phase mismatch and the input power, such two-color defect modes can be realized in three different localized states. We also study resonant light scattering in the arrays with the defect waveguide.Comment: 10 pages, 3 figures, published in PR

Fano resonance in quadratic waveguide arrays

We study resonant light scattering in arrays of channel optical waveguides where tunable quadratic nonlinearity is introduced as nonlinear defects by periodic poling of single (or several) waveguides in the array. We describe novel features of wave scattering that can be observed in this structure and show that it is a good candidate for the first observation of Fano resonance in nonlinear optics.Comment: 3 pages, 3 figures, submitted to Optics Letters, slightly revise

Spatial rogue waves in photorefractive SBN crystals

We report on the excitation of large-amplitude waves, with a probability of around 1% of total peaks, on a photorefractive SBN crystal by using a simple experimental setup at room temperature. We excite the system using a narrow Gaussian beam and observe different dynamical regimes tailored by the value and time rate of an applied voltage. We identify two main dynamical regimes: a caustic one for energy spreading and a speckling one for peak emergence. Our observations are well described by a two-dimensional Schr\"odinger model with saturable local nonlinearity.Comment: 4 pages, 4 figure

Nonlinear localized modes in dipolar Bose-Einstein condensates in optical lattices

The modulational instability and discrete matter wave solitons in dipolar BEC, loaded into a deep optical lattice, are investigated analytically and numerically. The process of modulational instability of nonlinear plane matter waves in a dipolar nonlinear lattice is studied and the regions of instability are established. The existence and stability of bulk discrete solitons are analyzed analytically and confirmed by numerical simulations. In a marked contrast with the usual DNLS behavior (no dipolar interactions), we found a region where the two fundamental modes are simultaneously unstable allowing enhanced mobility across the lattice for large norm values. To study the existence and properties of surface discrete solitons, an analysis of the dimer configuration is performed. The properties of symmetric and antisymmetric modes including the stability diagrams and bifurcations are investigated in closed form. For the case of a bulk medium, properties of fundamental on-site and inter-site localized modes are analyzed. On-site and inter-site surface localized modes are studied finding that they do not exist when nonlocal interactions predominate with respect to local ones.Comment: 12 pages, 13 figure

Surface gap solitons at fabricated photonic lattice interfaces

We generate surface gap solitons with staggered phase structure at the edge of a semi-infinite LiNbO3 waveguide array with defocusing nonlinearity. We characterize self- localization dynamics and identify the threshold power for soliton formation

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

Chilean wildfires: probabilistic prediction, emergency response and public communication

The 2016/17 wildfire season in Chile was the worst on record, burning more than 600,000 hectares. Whilst wildfires are an important natural process in some areas of Chile supporting its diverse ecosystems, wildfires are also one of the biggest threats to Chile’s unique biodiversity and it’s timber and wine industries. They also pose a danger to human life and property due to the sharp wildland-urban interface that exists in many Chilean towns and cities. Wildfires are however difficult to predict due to the combination of physical (meteorology, vegetation and fuel condition), and human (population density and awareness level) factors. Most Chilean wildfires are started due to accidental ignition by humans. This accidental ignition could be minimized if an effective wildfire warning system alerted the population to the heightened danger of wildfires in certain locations and meteorological conditions. Here we demonstrate the design of a novel probabilistic wildfire prediction system. The system uses ensemble forecast meteorological data together with a longtime series of fire products derived from Earth Observation to predict not only fire occurrence, but in addition, how intense wildfires could be. The system provides wildfire risk estimation and associated uncertainty for up to 6 days in advance, and communicates it to a variety of end users. The advantage of this probabilistic wildfire warning system over deterministic systems is that it allows users to assess the confidence of a forecast and thus make more informed decisions regarding resource allocation and forest management. The approach used in this study could easily be adapted to communicate other probabilistic forecasts of natural hazards

Scattering of slow-light gap solitons with charges in a two-level medium

The Maxwell-Bloch system describes a quantum two-level medium interacting with a classical electromagnetic field by mediation of the the population density. This population density variation is a purely quantum effect which is actually at the very origin of nonlinearity. The resulting nonlinear coupling possesses particularly interesting consequences at the resonance (when the frequency of the excitation is close to the transition frequency of the two-level medium) as e.g. slow-light gap solitons that result from the nonlinear instability of the evanescent wave at the boundary. As nonlinearity couples the different polarizations of the electromagnetic field, the slow-light gap soliton is shown to experience effective scattering whith charges in the medium, allowing it for instance to be trapped or reflected. This scattering process is understood qualitatively as being governed by a nonlinear Schroedinger model in an external potential related to the charges (the electrostatic permanent background component of the field).Comment: RevTex, 14 pages with 5 figures, to appear in J. Phys. A: Math. Theo