Showing papers by "Yuri S. Kivshar published in 2009"
TL;DR: The robust three-dimensional guiding of particles is demonstrated over the distances of a few millimeters of agglomerates of carbon nanoparticles with the size spanned from 100 nm to 10 microm, as well as their acceleration up to velocities of 1 cm/sec.
Abstract: We suggest a novel approach in all-optical trapping employing a photophoretic force for manipulation of absorbing particles in open air. We demonstrate experimentally the robust three-dimensional guiding, over the distances of a few millimeters, of agglomerates of carbon nanoparticles with the size spanned from 100 nm to 10μm, as well as their acceleration up to velocities of 1 cm/sec. We achieve stable positioning and guiding of particles as well as simultaneous trapping of a large number of particles in a dual beam optical trap created by two counter-propagating and co-rotating optical vortex beams.
200 citations
TL;DR: In this article, the authors propose an approach for tuning the transmission characteristics of metamaterials through a continuous adjustment of the lattice structure and confirm it experimentally in the microwave range.
Abstract: We propose an efficient approach for tuning the transmission characteristics of metamaterials through a continuous adjustment of the lattice structure and confirm it experimentally in the microwave range. The concept is rather general and applicable to various metamaterials as long as the effective medium description is valid. The demonstrated continuous tuning of a metamaterial response is highly desirable for a number of emerging applications of metamaterials, including sensors, filters, and switches, realizable in a wide frequency range.
174 citations
TL;DR: A theoretical approach for describing the optical trapping and manipulation of carbon nanoclusters in air with a dual-vortex optical trap is developed, and theoretical predictions with the experimental data are compared.
Abstract: We develop a theoretical approach for describing the optical trapping and manipulation of carbon nanoclusters in air with a dual-vortex optical trap, as realized recently in experiment [V. Shvedov et al., Opt. Express 17, 5743 (2009)]. We calculate both longitudinal and transverse photophoretic forces acting on a spherical absorbing particle, and then compare our theoretical predictions with the experimental data.
161 citations
TL;DR: In this paper, the first-order effect of the broadening of a wavepacket can be suppressed as it propagates through a periodic potential, and higher-order effects are seen for the first time in an optical pulse guided along curved photonic lattices.
Abstract: The broadening of a wave-packet can be suppressed as it propagates through a periodic potential. The first-order effect of this so-called dynamic localization has been seen in many different systems. Higher-order effects are now seen for the first time in an optical pulse guided along curved photonic lattices.
138 citations
TL;DR: Reflection and transmission of an arbitrarily polarized vortex beam on an interface separating two dielectric media are studied and general expressions for linear and angular Goos-Hänchen and Imbert-Fedorov shifts are derived.
Abstract: We study, analytically and numerically, reflection and transmission of an arbitrarily polarized vortex beam on an interface separating two dielectric media and derive general expressions for linear and angular Goos–Hanchen (GH) and Imbert–Fedorov shifts. We predict a novel vortex-induced GH shift and also reveal a direct connection between the spin-induced angular shifts and the vortex-induced linear shifts.
134 citations
TL;DR: The detailed dynamics of spin-to-orbital angular momentum conversion for a circularly polarized Gaussian beam propagating along the optical axis of a uniaxial crystal is studied theoretically and experimentally.
Abstract: We study theoretically and verify experimentally the detailed dynamics of spin-to-orbital angular momentum conversion for a circularly polarized Gaussian beam propagating along the optical axis of a uniaxial crystal. We extend the results to the case of white-light beams when each of the spectral components undergoes its own wavelength-dependent angular momentum conversion process.
128 citations
TL;DR: A simple, single beam method for determination of the topological charge of polychromatic optical vortices based on astigmatic transformation of singular optical beams, where the intensity pattern of a vortex beam acquires a form of dark stripes in the focal plane of a cylindrical lens.
Abstract: We introduce a simple, single beam method for determination of the topological charge of polychromatic optical vortices. It is based on astigmatic transformation of singular optical beams, where the intensity pattern of a vortex beam acquires a form of dark stripes in the focal plane of a cylindrical lens. The number of the dark stripes is equal to the modulus of the vortex topological charge, while the stripe tilt indicates the charge sign. We demonstrate experimentally the effectiveness of this technique by revealing complex topological structure of polychromatic singular beams.
112 citations
TL;DR: An analytical model for describing the evolution of spatial plasmon-solitons is developed and a good agreement with numerical results is observed.
Abstract: We study nonlinear propagation of surface plasmon polaritons along an interface between metal and nonlinear Kerr dielectric. We demonstrate numerically self-focusing of a plasmon beam at large powers and the formation of slowly decaying spatial soliton in the presence of losses. We develop an analytical model for describing the evolution of spatial plasmon-solitons and observe a good agreement with numerical results.
109 citations
TL;DR: Two types of second-harmonic frequency-scattering processes are observed from chi(2) nonlinear gratings, one of which is identified as Raman-Nath type nonlinear diffraction that is explained by applying only transverse phase-matching conditions and the other by the longitudinal phase matching only.
Abstract: This work was supported by the Australian Research
Council and Israeli Science Foundation. S.
Saltiel acknowledges the Nonlinear Physics Centre
for hospitality and support.
96 citations
TL;DR: In this article, the thermal conductivity of single-walled carbon nanotubes for the cases of an isolated nanotube and a nanoteutube interacting with a substrate was studied.
Abstract: We study numerically the thermal conductivity of single-walled carbon nanotubes for the cases of an isolated nanotube and a nanotube interacting with a substrate. We employ two different numerical methods: (i) direct modeling of the heat transfer by molecular-dynamics simulations and (ii) analysis of the equilibrium dynamics by means of the Green-Kubo formalism. For the numerical modeling of the effective interatomic interactions, we employ both the Brenner potentials and the intermolecular potentials used in the study of the dynamics of large macromolecules. We demonstrate that, quite independently of the methods employed and the potentials used, the character of the thermal conductivity depends crucially on the interaction between a nanotube and a substrate. While an isolated nanotube demonstrates anomalous thermal conductivity due to ballistic transport of long-wave acoustic phonons, the nanotube interacting with a flat substrate displays normal thermal conductivity due to both the appearance of a gap in the frequency spectrum of acoustic phonons and the absorption of long-wave acoustic phonons by the substrate. We study the dependence of the thermal conductivity on chirality, radius, and temperature of the single-walled carbon nanotubes in both the regimes and compare our findings with experimental data and earlier theoretical results for the thermal conductivity.
82 citations
TL;DR: In this paper, a new type of nonlinear metamaterials exhibiting a resonant electric response at microwave frequencies was proposed and designed, which is able to shift the frequency of the electric mode stop band by changing the incident power without affecting the magnetic response.
Abstract: We propose and design a new type of nonlinear metamaterials exhibiting a resonant electric response at microwave frequencies. By introducing a varactor diode as a nonlinear element within each resonator, we are able to shift the frequency of the electric mode stop band by changing the incident power without affecting the magnetic response. These elements could be combined with the previously developed nonlinear magnetic metamaterials in order to create negative index media with a control over both electric and magnetic nonlinearities.
TL;DR: In this paper, the authors study surface Tamm states in magnetophotonic structures magnetized in the Cotton-Mouton (Voigt) geometry and demonstrate that the violation of the time reversal symmetry due to the presence of magneto-optical materials gives rise to nonreciprocality of the surface modes.
Abstract: We study surface Tamm states in magnetophotonic structures magnetized in the Cotton–Mouton (Voigt) geometry. We demonstrate that the periodicity violation due to the structure truncation together with the violation of the time reversal symmetry due to the presence of magneto-optical materials gives rise to nonreciprocality of the surface modes. Dispersion of forward and backward modes splits and becomes magnetization dependent. This results in the magnetization-induced transitions between bulk and surface modes and unidirectional propagation of surface waves.
TL;DR: In this article, the authors demonstrate how to achieve reversible non-reciprocal optical response in a periodic photonic structure with a pair of defects, one of them being a nonlinear liquid crystal defect layer.
Abstract: We demonstrate how to achieve reversible nonreciprocal optical response in a periodic photonic structure with a pair of defects, one of them being a nonlinear liquid crystal defect layer. The twin defect layers structure is symmetric at low intensity and becomes asymmetric above a power threshold corresponding to the optical reordering of the liquid crystal. We show that nonreciprocal effects can be reversed by changing the wavelength as a consequence of the defect mode dependent light localization inside the structure.
TL;DR: In this article, the existence and stability of spatial vortex solitons in two-dimensional hexagonal photonic lattices was investigated and it was shown that the stability of the double-charge vortices is a consequence of the intersite power exchange in the vortex soliton and provided a simple stability criterion on the basis of the analysis of the corresponding discrete nonlinear model.
Abstract: We report on the experimental observation of stable double-charge discrete vortex solitons generated in hexagonal photonic lattices created optically in self-focusing nonlinear media and show that single-charge vortex solitons are unstable in analogous conditions. Subsequently, we study, both theoretically and experimentally, the existence and stability of spatial vortex solitons in two-dimensional hexagonal photonic lattices. We demonstrate that the stability of the double-charge vortices is a consequence of the intersite power exchange in the vortex soliton, and we provide a simple stability criterion on the basis of the analysis of the corresponding discrete nonlinear model. We extend our analysis to the case of defocusing nonlinearity and show the inversion of the vortex stability properties resulting in the fact that single-charge vortices become stable while their double-charge counterparts are unstable.
TL;DR: In this paper, a diode with tunable and nonlinear capacitance was introduced to demonstrate nonlinear control of the ENZ tunneling by an external field, as well as self-modulation of the transmission resonance due to the incident wave.
Abstract: The epsilon-near-zero (ENZ) tunneling phenomenon allows full transmission of waves through a narrow channel even in the presence of a strong geometric mismatch. Here we experimentally demonstrate nonlinear control of the ENZ tunneling by an external field, as well as self-modulation of the transmission resonance due to the incident wave. Using a waveguide section near cut-off frequency as the ENZ system, we introduce a diode with tunable and nonlinear capacitance to demonstrate both these effects. Our results confirm earlier theoretical ideas on using an ENZ channel for dielectric sensing and their potential applications for tunable slow-light structures.
TL;DR: This work employs liquid-infiltrated photonic crystal fibers and shows how the system geometry can modify the effective response of a nonlocal medium and the properties of two-dimensional gap solitons.
Abstract: We demonstrate, both theoretically and experimentally, the existence of nonlocal gap solitons in two-dimensional periodic photonic structures with defocusing thermal nonlinearity. We employ liquid-infiltrated photonic crystal fibers and show how the system geometry can modify the effective response of a nonlocal medium and the properties of two-dimensional gap solitons.
TL;DR: It is revealed that quadratic phase matching between the plasmon modes of different symmetries becomes possible in planar waveguide geometries, and second-harmonic generation can be achieved for interacting plAsmonic modes.
Abstract: The authors acknowledge a support of the Australian Research Council, and enlightened discussions
with D. Gramotnev and N. Zheludev.
TL;DR: It is demonstrated that the nonlocal, nonlinear response can dramatically enhance the field coupling leading to the stabilization of the vortex beam when the amplitude of the second beam exceeds some threshold value.
Abstract: We analyze the existence and stability of two-component vector solitons in nematic liquid crystals for which one of the components carries angular momentum and describes a vortex beam. We demonstrate that the nonlocal, nonlinear response can dramatically enhance the field coupling leading to the stabilization of the vortex beam when the amplitude of the second beam exceeds some threshold value. We develop a variational approach to describe this effect analytically.
TL;DR: In this article, the dispersion properties of electromagnetic Bloch waves in semi-infinite periodic structures created by alternating metamaterial and dielectric layers were studied in the long-wavelength limit.
Abstract: We study the properties of electromagnetic Bloch waves in semi-infinite periodic structures created by alternating metamaterial and dielectric layers. We derive and analyze the dispersion relations in the long-wavelength limit for both TE- and TM-polarized surface Bloch modes for magnetic metamaterials with negative refraction and metal-dielectric plasmonic superlattices. We reveal that in the subwavelength regime, the bulk modes are characterized by three different refractive indices (“trirefringence”), while the surface modes can propagate parallel to the Bloch wavevector and along the interface between superlattice and semi-infinite dielectric.
TL;DR: In this paper, the existence and properties of one-dimensional self-trapped beams spatial optical solitons in such media and demonstrate the existence of a bistability regime were analyzed.
Abstract: We study nonlinear light propagation in colloidal suspensions of spherical dielectric nanoparticles. We analyze the existence and properties of one-dimensional self-trapped beams spatial optical solitons in such media and demonstrate the existence of a bistability regime. The solitons corresponding to the two bistable branches have very different properties, and they can be easily distinguished by the measurement of the soliton width. We find that both types of solitons can form spontaneously through spatial modulational instability of continuous wave beams, but the solitons corresponding to the upper branch are more robust. This is also confirmed by the study of soliton collisions, where we describe a number of possible scenarios, including soliton amalgamation, destruction, reflection, deflection, and switching to another branch. We also find that the interaction of two mutually coherent solitons corresponding to different branches is phase independent and always repulsive. We provide a simple physical explanation of this phenomenon.
TL;DR: In this paper, the propagation of plasmon polaritons in one-dimensional chirped metal-dielectric layered structures has been studied and an optical Wannier-Stark ladder has been found in the mode spectrum and the energy flow may dramatically change its direction, thus providing possibilities for the beam steering in the transmission band.
Abstract: 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 © 2009 American Institute of Physics DOI: 101063/13119666 Recent technological advances opened up many opportunities for nanofabrication allowing one to study the fundamental effects earlier predicted only theoretically As an example, electronic Bloch oscillations predicted in 1928 Ref 1 were observed almost 50 years later, 2 when semiconductor superlattices with nanometer-scale thick layers were manufactured Nowadays, one of the most intriguing directions of research is associated with plasmon-polariton excitations and light manipulation at nanoscales 3,4 in various metal-dielectric structures, including multilayered periodic metal film stacks Periodic metal-dielectric stacks have been studied in a number of papers 5‐7 The studies of the transmission properties 6,7 revealed that such structures may exhibit resonant transmission due to plasmon tunneling through the structure This effect by itself is quite remarkable, since every second layer in the structure is made of metal, ie, it is opaque It was suggested that these structures can be used as spatial filters 7 Optical Bloch oscillations in periodic dielectric structures represent an analog of the electronic Bloch oscillations in crystals Such oscillations were observed in different dielectric structures, 8‐11 and they were also predicted to occur in metal-dielectric structures 12,13 where it was shown that the structures with spatially modulated refractive index of dielectric layers can exhibit optical Bloch oscillations 12 More complex heterostructures containing coupled dielectric cavities sandwiched between the metal-dielectric waveguides were also shown to exhibit Bloch oscillations, 13 somewhat similar to those observed in dielectric superlattices 11 In this letter we study the beam propagation in structures with linearly varying chirped thickness of the dielectric layers and uniform thickness of metallic layers We predict the possibility of plasmonic Bloch oscillations arising due to the excitation and coupling of plasmon polaritons We show that the energy flow can change its direction within one period of oscillations, leading to the beam curling similar to that predicted for layered structures with left-handed metamaterials 14 Such flexibility of beam control can open up opportunities of the light manipulation on nanoscales We start our analysis by studying periodic onedimensional stack consisting of thin metal layers of the width h separated by layers of conventional dielectric of the width l, so that the period of the structure is defined as =h+l The refractive index in one unit-cell of the structure is written as
TL;DR: In this article, parametric amplification in nonlinear left-handed transmission lines, which serve as model systems for nonlinear negative-index metamaterials, is studied. And the authors demonstrate the amplification of the incident wave by up to 15 dB in the left-hand regime.
Abstract: We study parametric amplification in nonlinear left-handed transmission lines, which serve as model systems for nonlinear negative-index metamaterials. We experimentally demonstrate the amplification of a weak signal in the three following regimes: with the signal in the left-handed band, with the signal in the stop band, and with the signal at a defect frequency. In particular, we demonstrate the amplification of the incident wave by up to 15 dB in the left-handed regime.
TL;DR: It is demonstrated that disorder allows realizing broadband third-harmonic generation via cascading of two second-order quasi-phase matched nonlinear processes.
Abstract: We study parametric frequency conversion in quadratic nonlinear media with disordered ferroelectric domains. We demonstrate that disorder allows realizing broadband third-harmonic generation via cascading of two second-order quasi-phase matched nonlinear processes. We analyze both spatial and polarization properties of the emitted radiation and find the results in agreement with our theoretical predictions.
TL;DR: In this article, the authors studied self-trapped localized nonlinear states in the form of truncated Bloch waves in one-dimensional optical lattices, which appear in the gaps of the linear band-gap spectrum.
Abstract: We study self-trapped localized nonlinear states in the form of truncated Bloch waves in one-dimensional optical lattices, which appear in the gaps of the linear band-gap spectrum. We demonstrate the existence of families of such localized states which differ by the number of intensity peaks. These families do not bifurcate from the band edge, and their power curves exhibit double branches. Linear-stability analysis demonstrates that in deep lattice potentials, the states corresponding to the lower branches are stable, whereas those corresponding to the upper branches are unstable, independently of the number of peaks.
TL;DR: In this paper, the interaction of two optical beams of different wavelengths colors in a nematic liquid crystal was studied, and it was shown that a beam in one color can stabilize a vortex in the other color, the vortex being unstable in the absence of the second beam.
Abstract: We study the interaction of two optical beams of different wavelengths colors in a nematic liquid crystal. We consider the case for which one component carries an optical vortex and the other component describes a localized beam. It is shown that a beam in one color can stabilize a vortex in the other color, the vortex being unstable in the absence of the second beam. We also show that the bright vortex can guide the beam in a stable manner, provided that the nonlocality is large enough. In this context we find that a different type of solitary wave nematicon instability can arise, one for which a ring structure develops at its peak. The results of approximate modulation solutions for the interaction between the vortex and the beam are found to be in good quantitative agreement with direct numerical simulations.
TL;DR: In this paper, the propagation of higher-order two-dimensional spatial solitons in optical media with nonlocal thermal nonlinear response was studied, and it was shown that these localized states experience complex dynamics including transformations between solitONS of different symmetries which depend strongly on the geometry of a nonlinear sample.
Abstract: We study theoretically the propagation of higher-order two-dimensional spatial solitons in optical media with nonlocal thermal nonlinear response. We show that these localized states experience complex dynamics including transformations between solitons of different symmetries which depend strongly on the geometry of a nonlinear sample. Boundaries exert repulsive forces on a soliton and, depending on its initial position relative to the boundaries, we observe transverse motion of a beam as a whole across the sample, effectively facilitating transformations.
TL;DR: In this article, the structure of spin-one Bose-Einstein condensates in the presence of a homogeneous magnetic field is analyzed and phase separation can occur in the ground state of antiferromagnetic (polar) condensate while the spin components of the ferromagnetic component are always miscible and no phase separation occurs.
Abstract: We analyze the structure of spin-one Bose-Einstein condensates in the presence of a homogeneous magnetic field We classify the homogeneous stationary states and study their existence, bifurcations, and energy spectra We reveal that phase separation can occur in the ground state of antiferromagnetic (polar) condensates while the spin components of the ferromagnetic condensates are always miscible and no phase separation occurs Our theoretical model, confirmed by numerical simulations, explains that this phenomenon takes place when the energy of the lowest homogeneous state is a concave function of the magnetization In particular, we predict that phase separation can be observed in a $^{23}\text{N}\text{a}$ condensate confined in a highly elongated harmonic trap Finally, we discuss the phenomena of dynamical instability and spin domain formation
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TL;DR: In this article, the propagation and localization of classical waves in one-dimensional disordered structures composed of alternating layers of left and right-handed materials (mixed stacks) and compare them to the structure composed of different layers of the same material (homogeneous stacks).
Abstract: We study the propagation and localization of classical waves in one-dimensional disordered structures composed of alternating layers of left- and right-handed materials (mixed stacks) and compare them to the structures composed of different layers of the same material (homogeneous stacks). For weakly scattering layers, we have developed an effective analytical approach and have calculated the transmission length within a wide region of the input parameters. When both refractive index and layer thickness of a mixed stack are random, the transmission length in the long-wave range of the localized regime exhibits a quadratic power wavelength dependence with the coefficients different for mixed and homogeneous stacks. Moreover, the transmission length of a mixed stack differs from reciprocal of the Lyapunov exponent of the corresponding infinite stack. In both the ballistic regime of a mixed stack and in the near long-wave region of a homogeneous stack, the transmission length of a realization is a strongly fluctuating quantity. In the far long-wave part of the ballistic region, the homogeneous stack becomes effectively uniform and the transmission length fluctuations are weaker. The crossover region from the localization to the ballistic regime is relatively narrow for both mixed and homogeneous stacks. In mixed stacks with only refractive-index disorder, Anderson localization at long wavelengths is substantially suppressed, with the localization length growing with the wavelength much faster than for homogeneous stacks. The crossover region becomes essentially wider and transmission resonances appear only in much longer stacks. All theoretical predictions are in an excellent agreement with the results of numerical simulations.
TL;DR: The results to the oblique incidence case are extended and experimentally the optimal parameters for generation of a single charge on-axis optical vortex are confirmed, including spectrally resolved measurements for the white-light beams.
Abstract: We report on the experimental and theoretical investigation of polarization conversion of linearly polarized Gaussian beam propagating in perpendicularly cut homogeneous uniaxial crystals. We derive analytical expressions, in good agreement with experimental data, for power transfer between components at normal incidence accompanied by the generation of a topological quadrupole. We extend the results to the oblique incidence case and confirm experimentally the optimal parameters for generation of a single charge on-axis optical vortex, including spectrally resolved measurements for the white-light beams.