Thresholdless surface solitons

We report on the existence of nonlinear surface waves which, on the one hand, do not require the threshold energy flow for their excitation, and, on the other hand, extend into media at both sides of the interface at low powers, i.e. can not be reduced to the conventional Tamm states. Such waves can be excited if the refractive index in at least one of the materials forming the interface is periodically modulated, with properly selected modulation depth and frequency. Thresholdless surface solitons can be stable in the entire existence domain.Comment: 3 pages, 4 figures, to appear in Optics Letter

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

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

Two-color surface lattice solitons

We study the properties of surface solitons generated at the edge of a semi-infinite photonic lattice in nonlinear quadratic media, namely two-color surface lattice solitons. We analyze the impact of phase mismatch on existence and stability of surface modes, and find novel classes of two-color twisted surface solitons which are stable in a large domain of their existence.Comment: 4 pages, 5 figures, Submitted for publicatio

Bloch wavepacket control in truncated modulated optical lattices

We study the reflection of Bloch wavepackets at the interface of optical lattice possessing a shallow longitudinal out-of-phase refractive index modulation in adjacent waveguides. We show that the relation between the transmitted and reflected energy flows can be efficiently controlled by tuning the frequency and the depth of the modulation. Thus, complete beam reflection may be achieved for a set of resonant modulation frequencies at which light tunneling between adjacent guides of modulated lattice is inhibited.Comment: 14 pages, 4 figures, to appear in Optics Letter

Interface solitons in two-dimensional photonic lattices

We analyze localization of light at the interface separating square and hexagonal photonic lattices, as recently realized experimentally in two-dimensional laser-written waveguide arrays in silica glass with self-focusing nonlinearity [A. Szameit {\em et al.}, Opt. Lett. {\bf 33}, 663 (2008)]. We reveal the conditions for the existence of {\em linear} and {\em nonlinear} surface states substantially influenced by the lattice topology, and study the effect of the different symmetries and couplings on the stability of two-dimensional interface solitons.Comment: 3 pages, 4 figures, submitted to Opt. Let

Genesis of Flea-Born Transmission of Plague Microbe, Yersinia pestis: Two Approachs – Molecular-Genetic and Ecological Ones

Two approaches to studying the origin and transmission mechanism of the flea-borne plague pathogen, Yersinia pestis: molecular-genetic and ecological ones – are considered in this review. The molecular genetic approach is based on saltation evolutionary ideology and relies upon the phenomenon of horizontal gene transfer of pla and ymt as critical evolutionary events. Further deletion of some structural and regulatory genes optimized “blockage” mechanism of transmission. The Ecological approach is based on the modern synthetic theory of evolution. It posits a gradual population-genetic transformation in the Marmot – Flea (Marmota sibirica – Oropsylla silantiewi) transitional (heterothermal, heteroimmune) host-parasite system in Late Pleistocene – Holocene epochs. The best prospects for disclosing the mechanisms of evolutionary formation of flea-borne Y. pestis transmission consist in the synthesis of molecular-genetic and ecological approaches

Molecular phylogenies of the plague microbe <i>Yersinia pestis</i>: an environmental assessment

Two approaches are applied to studies of the phylogeny of the plague microbe Yersinia pestis, i.e., the reconstruction of its history: Molecular genetic (MG) and ecological (ECO). The MG approach dominates. Phylogenies created with MG and ECO methods are not congruent. MG conclusions contradict the known facts and patterns of ecology, biogeography, paleontology, etc. We discuss some obvious contradictions and inconsistencies and suggest that real phylogenies of the plague microbe can be constructed only on the basis of the integration of MG and ECO approaches

Nonlinear localized modes at phase-slip defects in waveguide arrays

We study light localization at a phase-slip defect created by two semi-infinite mismatched identical arrays of coupled optical waveguides. We demonstrate that the nonlinear defect modes possess the specific properties of both nonlinear surface modes and discrete solitons. We analyze stability of the localized modes and their generation in both linear and nonlinear regimes.Comment: 3 pages, 6 figures, submitted to Opt. Let