Showing papers by "Yuri S. Kivshar published in 2008"
TL;DR: In this article, the properties of a tunable nonlinear metamaterial operating at microwave frequencies were investigated, where a varactor diode is introduced into each resonator so that the magnetic resonance can be tuned dynamically by varying the input power.
Abstract: We study the properties of a tunable nonlinear metamaterial operating at microwave frequencies We fabricate the nonlinear metamaterial composed of double split-ring resonators and wires where a varactor diode is introduced into each resonator so that the magnetic resonance can be tuned dynamically by varying the input power We show that at higher powers the transmission of the metamaterial becomes power dependent, and we demonstrate experimentally power-dependent transmission properties and selective generation of higher harmonics
149 citations
TL;DR: It is shown that the conical beams are formed as a result of the higher-order nonlinear Bragg diffraction involving two parametric processes in which an ordinary fundamental wave is converted simultaneously into ordinary and extraordinary polarized second harmonics.
Abstract: We report on the observation of second-harmonic conical waves generated in a novel geometry of the transverse excitation of an annular periodically poled nonlinear photonic structure by a fundamental Gaussian beam. We show that the conical beams are formed as a result of the higher-order nonlinear Bragg diffraction involving two parametric processes in which an ordinary fundamental wave is converted simultaneously into ordinary and extraordinary polarized second harmonics.
130 citations
TL;DR: Deep connections between the resonances in the continuous and discrete systems are revealed and an exactly solvable one-dimentional discrete model with nonlocal coupling for simulating diffraction in wave scattering in systems with reduced spatial dimensionality is introduced.
Abstract: The conditions for observing Fano resonances at elastic light scattering by a single finite-size obstacle are discussed. General arguments are illustrated by consideration of the scattering by a small (relative to the incident light wavelength) spherical obstacle based upon the exact Mie solution of the diffraction problem. The most attention is paid to recently discovered anomalous scattering. An exactly solvable one-dimentional discrete model with nonlocal coupling for simulating diffraction in wave scattering in systems with reduced spatial dimensionality is also introduced and analyzed. Deep connections between the resonances in the continuous and discrete systems are revealed.
120 citations
TL;DR: In this article, 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 and Imbert-Fedorov shifts are studied.
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 and Imbert-Fedorov shifts. We predict a novel vortex-induced Goos-Hanchen shift, and also reveal direct connection between the spin-induced angular shifts and the vortex-induced linear shifts.
115 citations
TL;DR: Nonlinear modes in a subwavelength slot waveguide created by a nonlinear dielectric slab sandwiched between two metals reveal that the symmetric mode undergoes the symmetry-breaking bifurcation and becomes primarily localized near one of the interfaces.
Abstract: We study nonlinear modes in a subwavelength slot waveguide created by a nonlinear dielectric slab sandwiched between two metals. We present the dispersion diagrams of the families of nonlinear guided modes and reveal that the symmetric mode undergoes the symmetry-breaking bifurcation and becomes primarily localized near one of the interfaces. We also find that the antisymmetric mode may split into two brunches giving birth to two families of nonlinear antisymmetric modes.
115 citations
TL;DR: It is demonstrated that at higher powers the transmission of the metamaterial becomes power-dependent and, as a result, such meetamaterial can demonstrate various nonlinear properties.
Abstract: We study experimentally nonlinear tunable magnetic metamaterials operating at microwave frequencies. We fabricate the nonlinear metamaterial composed of double split-ring resonators where a varactor diode is introduced into each resonator so that the magnetic resonance can be tuned dynamically by varying the input power. We demonstrate that at higher powers the transmission of the metamaterial becomes power-dependent and, as a result, such metamaterial can demonstrate various nonlinear properties. In particular, we study experimentally the power-dependent shift of the transmission band and demonstrate nonlinearity-induced enhancement (or suppression) of wave transmission.
107 citations
TL;DR: It is demonstrated the existence of a broad class of higher-order rotating spatial solitons in nonlocal nonlinear media and the tripole soliton carrying two spiraling phase dislocations, or self-trapped optical vortices.
Abstract: We demonstrate the existence of a broad class of higher-order rotating spatial solitons in nonlocal nonlinear media. We employ the generalized Hermite-Laguerre-Gaussian ansatz for constructing multivortex soliton solutions and study numerically their dynamics and stability. We discuss in detail the tripole soliton carrying two spiraling phase dislocations, or self-trapped optical vortices.
85 citations
TL;DR: A novel effect of the coupled-resonator-induced reflection (CRIR) characterized by a very high and easily tunable quality factor of the reflection line, for the case of the inter-site coupling between the cavities and the waveguide.
Abstract: We study the resonant transmission of light in a coupled-resonator optical waveguide interacting with two nearly identical side cavities. We reveal and describe a novel effect of the coupled-resonator-induced reflection (CRIR) characterized by a very high and easily tunable quality factor of the reflection line, for the case of the inter-site coupling between the cavities and the waveguide. This effect differs sharply from the coupled-resonator-induced transparency (CRIT)--an all-optical analogue of the electromagnetically-induced transparency--which has recently been studied theoretically and experimentally for the structures based on micro-ring resonators and photonic crystal cavities. Both CRIR and CRIT effects have the same physical origin which can be attributed to the Fano-Feshbach resonances in the systems exhibiting more than one resonance. We discuss the applicability of the novel CRIR effect to the control of the slow-light propagation and low-threshold all-optical switching.
76 citations
TL;DR: It is demonstrated that topological stabilization of such nonlinear localized states can be achieved through self-trapping of truncated two-dimensional Bloch waves and numerical simulations of the beam propagation in weakly deformed lattice potentials in anisotropic photorefractive media confirm the experimental results.
Abstract: We report on the first observation of topologically stable spatially localized multivortex solitons generated in optically induced hexagonal photonic lattices. We demonstrate that topological stabilization of such nonlinear localized states can be achieved through self-trapping of truncated two-dimensional Bloch waves and confirm our experimental results by numerical simulations of the beam propagation in weakly deformed lattice potentials in anisotropic photorefractive media.
73 citations
TL;DR: The results demonstrate that the degree of surface wave localization can be controlled by selecting the waveguide bending amplitude, and generate the linear surface modes in truncated arrays of periodically curved optical waveguides created in fused silica by a laser direct-writing technique.
Abstract: We report on the experimental observation of novel defect-free surface modes predicted theoretically for modulated photonic lattices [I. L. Garanovich et al., Phys. Rev. Lett. 100, 203904 (2008)10.1103/PhysRevLett.100.203904]. We generate the linear surface modes in truncated arrays of periodically curved optical waveguides created in fused silica by a laser direct-writing technique. Our results demonstrate that the degree of surface wave localization can be controlled by selecting the waveguide bending amplitude.
65 citations
TL;DR: A novel model for the nonlinear response of colloids is introduced which describes consistently the system in the regimes of low and high light intensities and low/large concentrations of colloidal particles.
Abstract: We study nonlinear light propagation in colloidal nanosuspensions. We introduce a novel model for the nonlinear response of colloids which describes consistently the system in the regimes of low and high light intensities and low/large concentrations of colloidal particles. We employ this model to study the light-induced instabilities and demonstrate the formation of stable spatial solitons as well as the existence of a bistability regime.
TL;DR: In this paper, the formation of discrete diffraction-managed optical solitons in arrays of periodically curved coupled waveguides was observed for two types of modulated structures: laser-written arrays in silica glass and lithium niobate waveguide arrays with self-defocusing photorefractive nonlinearity.
Abstract: We observe the formation of discrete diffraction-managed optical solitons in arrays of periodically curved coupled waveguides for two types of modulated structures: laser-written arrays in silica glass with self-focusing nonlinearity and lithium niobate waveguide arrays with self-defocusing photorefractive nonlinearity. Our results demonstrate that, for both types of nonlinear response, soliton formation occurs after transitional self-induced beam broadening, being fundamentally different from nonlinear self-focusing and defocusing in a bulk medium or discrete self-trapping in straight waveguides.
TL;DR: It is found that the average velocity of a soliton and the soliton current induced by the ratchet depend on the number of atoms in thesoliton, and soliton transport can be induced through scattering of different solitons.
Abstract: We study the dynamics of bright solitons formed in a Bose-Einstein condensate with attractive atomic interactions perturbed by a weak bichromatic optical lattice potential. The lattice depth is a biperiodic function of time with a zero mean, which realizes a flashing ratchet for matter-wave solitons. We find that the average velocity of a soliton and the soliton current induced by the ratchet depend on the number of atoms in the soliton. As a consequence, soliton transport can be induced through scattering of different solitons. In the regime when matter-wave solitons are narrow compared to the lattice period the dynamics is well described by the effective Hamiltonian theory.
TL;DR: This paper concludes the Focus Serial assembled of invited papers in key areas of nonlinear optics ( edited by J.M. Dudley and R.W. Boyd), and it discusses new directions for future research in this field.
Abstract: This paper concludes the Focus Serial assembled of invited papers in key areas of nonlinear optics (Editors: J.M. Dudley and R.W. Boyd), and it discusses new directions for future research in this field.
TL;DR: A modified mean-field theory is developed and the properties of these novel cavity solitons demonstrating, in particular, their substantial narrowing in the zero-diffraction regime are analyzed.
Abstract: We predict a novel type of cavity solitons, Bloch cavity solitons, existing in nonlinear resonators with the refractive index modulated in both longitudinal and transverse directions and for both focusing (at normal diffraction) and defocusing (at anomalous diffraction) nonlinearities. We develop a modified mean-field theory and analyze the properties of these novel cavity solitons demonstrating, in particular, their substantial narrowing in the zero-diffraction regime.
TL;DR: It is predicted that interfaces of periodically curved waveguide arrays can support a novel type of surface states which exist in a certain region of modulation parameters associated with the band flattening, and it is shown that the existence of these modes in different band gaps can be flexibly controlled by selecting the modulation profile.
Abstract: We predict that interfaces of periodically curved waveguide arrays can support a novel type of surface states which exist in a certain region of modulation parameters associated with the band flattening. Such linear surface states appear in truncated but otherwise perfect (defect-free) lattices as a direct consequence of the periodic modulation of the lattice potential. We show that the existence of these modes in different band gaps can be flexibly controlled by selecting the modulation profile, with no restrictions on Bloch-wave symmetries characteristic of Shockley states.
TL;DR: In this article, the authors studied large-amplitude oscillations of carbon nanotubes with chiralities and predicted the existence of spatially localized nonlinear modes in the form of discrete breathers.
Abstract: We study large-amplitude oscillations of carbon nanotubes with chiralities (m, 0) and (m, m) and predict the existence of spatially localized nonlinear modes in the form of discrete breathers. In nanotubes with the index (m, 0) we find three types of discrete breathers associate with longitudinal, radial, and torsion anharmonic vibrations, however only the twisting breathers are found to be nonradiating nonlinear modes which survive in a curved geometry described by a three-dimensional microscopic model and remain long-lived modes even in the presence of thermal fluctuations.
TL;DR: In this paper, the authors demonstrate that one-dimensional photonic crystals with pure nematic liquid-crystal defects can operate as all-optical switching devices based on optical orientational nonlinearities of liquid crystals.
Abstract: We demonstrate that one-dimensional photonic crystals with pure nematic liquid-crystal defects can operate as all-optical switching devices based on optical orientational nonlinearities of liquid crystals. We show that such a periodic structure is responsible for a modulated threshold of the optical Freedericksz transition in the spectral domain, and this leads to all-optical switching and light-induced multistability. This effect has no quasistatics electric field analog, and it results from nonlinear coupling between light and a defect mode. © 2008 American Institute of Physics. DOI: 10.1063/1.2949076
TL;DR: The implementation of this parametric process for characterisation of femtosecond pulses is demonstrated, enabling the estimation of pulse width, chirp, and front tilt through monitoring the evolution of the autocorrelation trace inside the nonlinear crystal.
Abstract: We study experimentally the process of the second harmonic generation by two noncollinear beams in quadratic nonlinear crystals with a disordered structure of ferroelectric domains. We show that the second-harmonic radiation is emitted in the form of two cones as well as in a plane representing the cross-correlation of the two fundamental pulses. We demonstrate the implementation of this parametric process for characterisation of femtosecond pulses, enabling the estimation of pulse width, chirp, and front tilt. This is achieved through monitoring the evolution of the autocorrelation trace inside the nonlinear crystal.
TL;DR: This work implements experimentally a simple method based on the polarimetric technique for recording the polarization maps of vector fields, where coaxial superposition of orthogonally polarized reference and signal beams allows the signal phase to be reconstructed from the polarization map of the total field.
Abstract: We implement experimentally a simple method for accurate measurements of phase distributions of scalar light fields. The method is based on the polarimetric technique for recording the polarization maps of vector fields, where coaxial superposition of orthogonally polarized reference and signal beams allows the signal phase to be reconstructed from the polarization map of the total field. We demonstrate this method by resolving topologically neutral pairs of closely positioned vortices in a speckle field and recovering the positions of vortices within a Laguerre-Gaussian beam with the topological charge three.
TL;DR: In this article, the authors studied many-body quantum coherence and interaction blockade in two Josephson-linked Bose-Einstein condensates and introduced universal operators for characterizing manybody coherence without limitations on the system symmetry and total particle number.
Abstract: We study many-body quantum coherence and interaction blockade in two Josephson-linked Bose-Einstein condensates. We introduce universal operators for characterizing many-body coherence without limitations on the system symmetry and total particle number N. We reproduce the results for both coherence fluctuations and number squeezing in symmetric systems of large N, and reveal several peculiar phenomena that may occur in asymmetric systems and systems of small N. For asymmetric systems, we show that, due to an interplay between asymmetry and inter-particle interaction, the coherence fluctuations are suppressed dramatically when |EC/EJ|1, and both resonant tunneling and interaction blockade take place for large values of |EC/EJ|, where EC and EJ are the interaction and tunneling energies, respectively. We emphasize that the resonant tunneling and interaction blockade may allow creating single-atom devices with promising technology applications. We demonstrate that for the systems at finite temperatures the formation of self-trapped states causes an anomalous behavior.
TL;DR: In this paper, a method of tuning the shift of the reflected beam in photonic crystals through modification of the surface, first structurally, as a change in the radius of surface rods, and then all-optically, with the addition of nonlinear material to the surface layer.
TL;DR: It is shown that the parameters of optical bottle beams generated from incoherent double-charge white-light vortices can be efficiently controlled by varying the beam focusing conditions.
Abstract: We generate experimentally optical bottle beams from incoherent double-charge white-light vortices, and show that their parameters can be efficiently controlled by varying the beam focusing conditions.
TL;DR: The existence of a class of nonlinear localized surface states, the so-called nonlinear Tamm states or surface breathers, which exhibit features that have no counterparts either in the continuous systems or in linear arrays are demonstrated.
Abstract: We analyze the properties of discrete breathers excited near the edge of a one-dimensional metamaterial created by a truncated array of nonlinear split-ring resonators. We study a crossover between nonlinear surface states and discrete breathers by analyzing the modes centered at finite distances from the array edge and demonstrate the existence of a class of nonlinear localized surface states, the so-called nonlinear Tamm states or surface breathers, which exhibit features that have no counterparts either in the continuous systems or in linear arrays.
TL;DR: This work was supported by the Australian Research Council under the Centres of Excellence Program and through the Australian Partnership for Advanced Computing National Facility (APAC), and part of this project was completed during the visit of A. V. Sukhorukov to McMaster University (Canada) supported by Australian======Academy of Science travel grant as mentioned in this paper.
Abstract: This work was supported by the Australian Research
Council under the Centres of Excellence Program
and through the Australian Partnership for Advanced
Computing National Facility (APAC). Part of this project
was completed during the visit of A. A. Sukhorukov to McMaster
University (Canada) supported by the Australian
Academy of Science travel grant. D. N. Chigrin acknowledges
partial support by the Deutsche Forschungsgemeinschaft
(DFG) through the project FOR 557. A. V. Laurinenko acknowledges partial support from European
Commission FP6, project NewTon, NMP4-CT-2005-
017160.
TL;DR: It is demonstrated that the nonlinear defect modes possess the specific properties of both nonlinear surface modes and discrete solitons and their generation in both linear and nonlinear regimes.
Abstract: 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 the stability of the localized modes and their generation in both linear and nonlinear regimes.
TL;DR: A novel concept of an inside-out (or inverse) cloak for electromagnetic waves based on the coordinate transformation of Maxwell's equations is introduced, which can be employed for creating absorbing non-reflecting media as matching layers in numerical simulations.
Abstract: We introduce a novel concept of an inside-out (or inverse) cloak for electromagnetic waves based on the coordinate transformation of Maxwell’s equations. This concept can be employed for creating absorbing non-reflecting media as matching layers in numerical simulations. In contrast to the commonly used perfectly matched layers, such absorbing boundaries are characterized by physically meaningful parameters, and the concept can be used in various numerical simulation schemes.
TL;DR: It is predicted that robust routing of slow-light pulses is possible between antisymmetrically coupled photonic-crystal waveguides and demonstrated that for all pulses with the group velocities varying by several orders of magnitude, the complete switching occurs at the fixed coupling length of just several unit cells of the photonic crystal.
Abstract: We suggest a novel and general approach to the design of photonic-crystal directional couplers operating in the slow-light regime. We predict, based on a general symmetry analysis, that robust tunneling of slow-light pulses is possible between antisymmetrically coupled photonic crystal waveguides. We demonstrate, through Bloch mode frequency-domain and finite-difference time-domain (FDTD) simulations that, for all pulses with strongly reduced group velocities at the photonic band-gap edge, complete switching occurs at a fixed coupling length of just a few unit cells of the photonic crystal.
TL;DR: In this paper, a two-dimensional magnetic metamaterial based on cut-wire pairs instead of split-ring resonators has been proposed for microwave frequency with lattice spacing around 10% of the free space wavelength.
Abstract: We study numerically and experimentally magnetic metamaterials based on cut-wire pairs instead of split-ring resonators. The cut-wire pair planar structure is extended in order to create a truly two-dimensional metamaterial suitable for scaling to optical frequencies. We fabricate the cut-wire metamaterial operating at microwave frequencies with lattice spacing around 10% of the free-space wavelength, and find good agreement with direct numerical simulations. Unlike the structures based on split-ring resonators, the nearest-neighbor coupling in cut-wire pairs can result in a magnetic stop-band with propagation in the transverse direction.
TL;DR: It is explained why collisions between two kinks and one antikink are observed to be practically elastic or strongly inelastic depending on relative initial positions of the kinks, and the fact that the three-soliton collisions become more elastic with an increase in the collision velocity becomes clear in the framework of thethree-particle model.
Abstract: We revisit the problem of the three-soliton collisions in the weakly perturbed sine-Gordon equation and develop an effective three-particle model allowing us to explain many interesting features observed in numerical simulations of the soliton collisions. In particular, we explain why collisions between two kinks and one antikink are observed to be practically elastic or strongly inelastic depending on relative initial positions of the kinks. The fact that the three-soliton collisions become more elastic with an increase in the collision velocity also becomes clear in the framework of the three-particle model. The three-particle model does not involve internal modes of the kinks, but it gives a qualitative description to all the effects observed in the three-soliton collisions, including the fractal scattering and the existence of short-lived three-soliton bound states. The radiationless energy exchange between the colliding solitons in weakly perturbed integrable systems takes place in the vicinity of the separatrix multi-soliton solutions of the corresponding integrable equations, where even small perturbations can result in a considerable change in the collision outcome. This conclusion is illustrated through the use of the reduced three-particle model.