Yuri S. Kivshar

Bio: Yuri S. Kivshar is an academic researcher from Australian National University. The author has contributed to research in topics: Metamaterial & Soliton. The author has an hindex of 126, co-authored 1845 publications receiving 79415 citations. Previous affiliations of Yuri S. Kivshar include Technische Universität Darmstadt & Los Alamos National Laboratory.

Bifurcations and stability of gap solitons in periodic potentials.

Abstract: We analyze the existence, stability, and internal modes of gap solitons in nonlinear periodic systems described by the nonlinear Schrodinger equation with a sinusoidal potential, such as photonic crystals, waveguide arrays, optically-induced photonic lattices, and Bose-Einstein condensates loaded onto an optical lattice. We study bifurcations of gap solitons from the band edges of the Floquet-Bloch spectrum, and show that gap solitons can appear near all lower or upper band edges of the spectrum, for focusing or defocusing nonlinearity, respectively. We show that, in general, two types of gap solitons can bifurcate from each band edge, and one of those two is always unstable. A gap soliton corresponding to a given band edge is shown to possess a number of internal modes that bifurcate from all band edges of the same polarity. We demonstrate that stability of gap solitons is determined by location of the internal modes with respect to the spectral bands of the inverted spectrum and, when they overlap, complex eigenvalues give rise to oscillatory instabilities of gap solitons.

Azimuthons: spatially modulated vortex solitons

Abstract: Recent progress in the experimental study of nonlinear optical effects in bulk dielectric media opens up many novel possibilities in the study of transverse self-trapping of light and the formation of spatial optical solitons [1]. Spatial optical solitons are stationary self-trapped localized modes in homogeneous self-focusing nonlinear media [2], and they may possess transverse energy flow associated with the complicated phase structure. Two familiar examples include radially symmetric vortex solitons [3,4] and rotating soliton clusters [5] created by several interacting fundamental solitons which rotate opposite to the phase gradient [6]. In this Letter, we introduce a novel class of spatially localized self-trapped optical beams in nonlinear media, the so-called azimuthons, which provide an important missing link between the radially symmetric vortices and rotating soliton clusters. We reveal novel physics of nontrivial rotation of self-trapped modulated optical beams and show that the associated angular momentum has two different contributions. The first contribution is due to the internal energy flow; it comes from a nontrivial phase as in the case of the radially symmetric vortex solitons; this reflects the wave nature of the self-trapped beams. The second contribution appears only when the rotating beam is modulated or fragmented, and it has a ‘‘particle’’ origin. While the latter contribution is important for the soliton clusters, the former one dominates for strongly overlapping beams when the ‘‘particle identity’’ in the beam structure is lost. Surprisingly, as we show below, these two contributions can be of opposite signs, giving birth to the nonrotating modulated singular beams described here as stationary azimuthons. In particular, we find the spatial solitons whose visible rotation can be directed alongside or opposite to the direction of the energy flow. Furthermore, the internal energy flow can be balanced exactly by the ‘‘mechanical’’ rotation, and, in this case, the truly stationary nonrotating states emerge. The term ‘‘azimuthons’’ for these novel selftrapped states reflects their distinctive modulated profile. The intensity of such states is a spatially localized ring modulated azimuthally, and the phase carries a screw-type dislocation; in contrast to the linear vortex phase � � m’, the phase of the azimuthon is a staircaselike nonlinear function of the polar angle ’. In other words, higher-order spatial solitons can be described in terms of azimuthal deformations of the vortex solitons. We analyze different families of such solutions in both Kerr and saturable nonlinear media and demonstrate that the azimuthons are characterized by two independent integer numbers or azimuthal indices: the topological charge m and the number of the intensity peaks N. For the soliton clusters [5,7], the number of peaks satisfies the condition N � 4m, while the rotating azimuthons with N � 2m can exist in saturable media; in particular, we demonstrate truly stationary nonrotating azimuthons with the indices m � 1 and N � 3. We consider the paraxial propagation of light in an isotropic nonlinear medium with an instantaneous re�

Metasurface Engineering through Bound States in the Continuum

Abstract: Optical systems provide a versatile platform for realizing different types of bound states in the continuum (BICs), thanks to advanced nanofabrication for photonic structures on demand. Optical BICs exhibit ultrahigh-$Q$ resonances, which can enhance light-matter interaction by orders of magnitude. Forming BICs in photonic crystals and metamaterials is usually associated with in-plane symmetry breaking, but here the authors break the $o\phantom{\rule{0}{0ex}}u\phantom{\rule{0}{0ex}}t\ensuremath{-}o\phantom{\rule{0}{0ex}}f\ensuremath{-}p\phantom{\rule{0}{0ex}}l\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}e$ symmetry in a dielectric metasurface's unit cell to control Fano resonances originating from quasi-BICs. This idea is found to be general, and confirmed experimentally for lattices of particle clusters of different symmetries.

All-Dielectric Resonant Meta-Optics Lightens up

Abstract: All-dielectric resonant nanophotonics is a rapidly developing research field driven by its exceptional applications for creating low-loss nanoscale metadevices. The tight confinement of the local e...

Dark solitons in nonlinear optics

Abstract: Recent theoretical and experimental results on propagation of dark-pulse solitons in nonlinear optical media are reviewed. Using an analytical approach based on the nonlinear Schrodinger equation, the authors describe properties of dark solitons, features of their generation by different input pulses, and the dynamics of dark solitons in the presence of perturbations. They also briefly discuss experimental results which show the possibility of dark-soliton propagation in optical fibers (temporal dark solitons), laser beams passed through a sodium vapor and nonlinear slab waveguides (spatial dark solitons), and demonstrate that theoretical predictions and experimental data are in good agreement. >

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Fast parallel algorithms for short-range molecular dynamics

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。