Showing papers by "Yuri S. Kivshar published in 2006"
TL;DR: It is demonstrated that the eigenfrequencies of the resonators can be tuned over a wide frequency range, and significantly, it is shown that the self-induced nonlinear effects observed in the varactor-loaded split-ring resonator structures can appear at relatively low power levels.
Abstract: We study experimentally the dynamic tunability and self-induced nonlinearity of split-ring resonators incorporating variable capacitance diodes. We demonstrate that the eigenfrequencies of the resonators can be tuned over a wide frequency range, and significantly, we show that the self-induced nonlinear effects observed in the varactor-loaded split-ring resonator structures can appear at relatively low power levels.
267 citations
TL;DR: The first experimental observation of photonic Bloch oscillations and Zener tunneling in two-dimensional periodic systems in a square lattice superimposed on a refractive index ramp is reported on.
Abstract: We report on the first experimental observation of photonic Bloch oscillations and Zener tunneling in two-dimensional periodic systems. We study the propagation of an optical beam in a square lattice superimposed on a refractive index ramp. We observe oscillations of the beam inside the first Brilloin zone and tunneling of light from the first to the higher-order bands of the lattice band gap spectrum.
223 citations
TL;DR: The crossover between linear repulsion and nonlinear attraction at the surface is studied, revealing the mechanism of nonlinearity-mediated stabilization of the surface gap modes.
Abstract: We report on the observation of surface gap solitons found to exist at the interface between uniform and periodic dielectric media with defocusing nonlinearity. We demonstrate strong self-trapping at the edge of a LiNbO3 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.
187 citations
TL;DR: The work was supported by the Australian Research Council and the Russian Fund for Basic Research (grant N05-02-16357) as discussed by the authors, and the authors acknowledge the warm hospitality of the Nonlinear Physics Centre during their stay in Canberra.
Abstract: The work was supported by the Australian Research
Council. Alexander Zharov acknowledges the warm hospitality
of the Nonlinear Physics Centre during his stay in
Canberra, as well as a support from the Russian Fund for
Basic Research (grant N05-02-16357).
177 citations
TL;DR: It is revealed that nonlocality can provide a simple physical mechanism for stabilization of multihump optical solitons and what is believed to be the first example of stable rotating dipole sol itons and soliton spiraling.
Abstract: We reveal that nonlocality can provide a simple physical mechanism for stabilization of multihump optical solitons and present what we believe to be the first example of stable rotating dipole solitons and soliton spiraling, which are known to be unstable in all types of realistic nonlinear media with a local response.
136 citations
TL;DR: In this paper, the authors demonstrate broadband femtosecond phase-matched noncollinear second-harmonic generation (SHG) in strontium barium niobate crystals with random ferroelectric domains.
Abstract: The authors demonstrate broadband femtosecond phase-matched noncollinear second-harmonic generation (SHG) in strontium barium niobate crystals with random ferroelectric domains. The process is similar to femtosecond SHG in ultrathin crystals, but it results in higher efficiency and exact mapping of the spectrum of the fundamental field into the spectrum of the second harmonics, even for pulses with complex spectral profiles. The observed parametric conversion process can be used as an efficient frequency mapping from infrared to visible for the femtosecond pulse monitoring.
131 citations
TL;DR: A crossover from nonlinear surface states to discrete solitons is studied by analyzing the families of odd and even modes centered at finite distances from the surface and the physical mechanism of the nonlinearity-induced stabilization of surface modes is revealed.
Abstract: We discuss the formation of self-trapped localized states near the edge of a semi-infinite array of nonlinear optical waveguides. We study a crossover from nonlinear surface states to discrete solitons by analyzing the families of odd and even modes centered at finite distances from the surface and reveal the physical mechanism of the nonlinearity-induced stabilization of surface modes.
113 citations
TL;DR: It is found that the discrete nature of the photonic crystal waveguides allows a geometry-driven enhancement of nonlinear effects by shifting the resonator location relative to the waveguide, thus providing an additional control of resonant waveguide transmission and Fano resonances.
Abstract: We analyze the resonant linear and nonlinear transmission through a photonic crystal waveguide sidecoupled to a Kerr-nonlinear photonic crystal resonator. First, we extend the standard coupled-mode theory analysis to photonic crystal structures and obtain explicit analytical expressions for the bistability thresholds and transmission coefficients which provide the basis for a detailed understanding of the possibilities associated with these structures. Next, we discuss limitations of standard coupled-mode theory and present an alternative analytical approach based on the effective discrete equations derived using a Green’s function method. We find that the discrete nature of the photonic crystal waveguides allows a geometry-driven enhancement of nonlinear effects by shifting the resonator location relative to the waveguide, thus providing an additional control of resonant waveguide transmission and Fano resonances. We further demonstrate that this enhancement may result in the lowering of the bistability threshold and switching power of nonlinear devices by several orders of magnitude. Finally, we show that employing such enhancements is of paramount importance for the design of all-optical devices based on slow-light photonic crystal waveguides.
92 citations
TL;DR: It is demonstrated that the recent observation of nonlinear self-trapping of matter waves in one-dimensional optical lattices can be associated with a novel type of broad nonlinear state existing in the gaps of the matter-wave band-gap spectrum.
Abstract: We demonstrate that the recent observation of nonlinear self-trapping of matter waves in one-dimensional optical lattices [Th. Anker et al., Phys. Rev. Lett. 94, 020403 (2005)] can be associated with a novel type of broad nonlinear state existing in the gaps of the matter-wave band-gap spectrum. We find these self-trapped localized modes in one-, two-, and three-dimensional periodic potentials, and demonstrate that such novel gap states can be generated experimentally in any dimension.
87 citations
TL;DR: It is demonstrated that even a weak microscopic disorder may lead to a substantial modification of the metamaterial magnetic properties, and a 10% deviation in the parameters of the microscopic resonant elements may leadto a substantial suppression of the wave propagation in a wide frequency range.
Abstract: We analyze the effect of microscopic disorder on the macroscopic properties of composite metamaterials and study how weak statistically independent fluctuations of the parameters of the structure elements can modify their collective magnetic response and left-handed properties. We demonstrate that even a weak microscopic disorder may lead to a substantial modification of the metamaterial magnetic properties, and a 10% deviation in the parameters of the microscopic resonant elements may lead to a substantial suppression of the wave propagation in a wide frequency range. A noticeable suppression occurs also if more than 10% of the resonant magnetic elements possess strongly different properties, and in the latter case the defects can create an additional weak resonant line. These results are of a key importance for characterizing and optimizing novel composite metamaterials with the left-handed properties at terahertz and optical frequencies.
76 citations
TL;DR: It is found that stable azimuthons become possible when the nonlocality parameter exceeds a certain threshold value and, in a sharp contrast to local media, the azimUTHons with N peaks can also exist for N < 2m, where m is the azIMuthon topological charge.
Abstract: We demonstrate that spatial nonlocal response provides an effective physical mechanism for stabilization of recently introduced azimuthally modulated self-trapped rotating singular optical beams or azimuthons [see A. S. Desyatnikov, A. A. Sukhorukov, and Yu. S. Kivshar, Phys. Rev. Lett. 95, 203904 (2005)]. We find that stable azimuthons become possible when the nonlocality parameter exceeds a certain threshold value and, in a sharp contrast to local media, the azimuthons with N peaks can also exist for N < 2m, where m is the azimuthon topological charge.
TL;DR: A novel type of localized beam supported by the combined effects of total internal and Bragg reflection in nonlinear two-dimensional square periodic structures showing strong anisotropy in their mobility properties is demonstrated.
Abstract: We demonstrate theoretically and experimentally a novel type of localized beam supported by the combined effects of total internal and Bragg reflection in nonlinear two-dimensional square periodic structures. Such localized states exhibit strong anisotropy in their mobility properties, being highly mobile in one direction and trapped in the other, making them promising candidates for optical routing in nonlinear lattices.
TL;DR: It is predicted that a sharp crossover from nonlinear self-defocusing to discrete self-trapping of a narrow Gaussian beam with the increase of the refractive index contrast in a periodic photonic lattice is predicted.
Abstract: We predict a sharp crossover from nonlinear self-defocusing to discrete self-trapping of a narrow Gaussian beam with the increase of the refractive index contrast in a periodic photonic lattice We demonstrate experimentally nonlinear discrete localization of light with defocusing nonlinearity by single site excitation in LiNbO3 waveguide arrays
TL;DR: In this article, the authors study the electromagnetic surface waves localized at an interface separating a one-dimensional photonic crystal and a left-handed metamaterial, the so-called surface Tamm states.
Abstract: The authors study the electromagnetic surface waves localized at an interface separating a one-dimensional photonic crystal and left-handed metamaterial, the so-called surface Tamm states. They demonstrate that the metamaterial allows for a flexible control of the dispersion properties of surface states and can support the Tamm states with a backward energy flow and a vortexlike structure.
TL;DR: P pulsed second harmonic generation in metamaterials under conditions of significant absorption is studied, predicting conversion efficiencies of 12% and 0.2% for attenuation lengths of 50 and 5microm, respectively.
Abstract: We study pulsed second harmonic generation in metamaterials under conditions of significant absorption. Tuning the pump in the negative index range, a second harmonic signal is generated in the positive index region, such that the respective indices of refraction have the same magnitudes but opposite signs. This insures that a forward-propagating pump is exactly phase matched to the backward-propagating second harmonic signal. Using peak intensities of ~500 MW/cm2, assuming χ(2)~80pm/V, we predict conversion efficiencies of 12% and 0.2% for attenuation lengths of 50 and 5µm, respectively.
TL;DR: It is demonstrated that the analysis of linear surface states in semi-infinite binary waveguide arrays provides important information about the existence of nonlinear surface modes and their properties.
Abstract: We analyze discrete surface modes in semi-infinite binary waveguide arrays, which can support simultaneously two types of discrete solitons We demonstrate that the analysis of linear surface states in such arrays provides important information about the existence of nonlinear surface modes and their properties We find numerically the families of both discrete surface solitons and nonlinear Tamm (gap) states and study their stability properties
TL;DR: It is demonstrated that, in contrast to the well-known optical quadrupoles generated by beams propagating along the optical axis of a uniaxial crystal, the beam bearing isolated single-charge on-axis vortex can be generated if the incident beam is tilted with respect to the opticalaxis at a certain angle.
Abstract: We implement a novel experimental technique for generating mono- and polychromatic optical beams with on-axis single vortex by manipulating polarization singularities of light in birefringent crystals. We demonstrate that, in contrast to the well-known optical quadrupoles generated by beams propagating along the optical axis of a uniaxial crystal, the beam bearing isolated single-charge on-axis vortex can be generated if the incident beam is tilted with respect to the optical axis at a certain angle.
TL;DR: This work predicts theoretically and generates in a photorefractive crystal two-dimensional self-trapped periodic waves of different symmetries, including vortex lattices-patterns of phase dislocations with internal energy flows, and demonstrates that these nonlinear waves exist even with anisotropic nonlocal nonlinearity when the optically-induced periodic refractive index becomes highly an isotropic.
Abstract: We predict theoretically and generate experimentally in pho-torefractive crystal two-dimensional self-trapped periodic waves of different symmetries, including vortex lattices – patterns of phase dislocations with internal energy flows. We demonstrate that these nonlinear waves exist with nonlocal nonlinearity even when the optically-induced periodic refractive index becomes highly anisotropic, and it depends on the orientation of the two-dimensional lattice relative to the crystallographic c-axis.
TL;DR: The local dispersion of the Bloch modes in the photonic lattice is probed by analyzing the linear diffraction of beams associated with the high-symmetry points of the Brillouin zone and the regimes of normal, anomalous, and anisotropic diffraction are distinguished through observations of nonlinear self-action effects.
Abstract: We generate experimentally different types of two-dimensional Bloch waves of a square photonic lattice by employing the phase imprinting technique.We probe the local dispersion of the Bloch modes in the photonic lattice by analyzing the linear diffraction of beams associated with the high-symmetry points of the Brillouin zone, and also distinguish the regimes of normal, anomalous, and anisotropic diffraction through observations of nonlinear self-action effects.
TL;DR: It is suggested that tunable orientational nonlinearity of nematic liquid crystals can be employed for all-optical switching in periodic photonic structures with liquid-crystal defects.
Abstract: We suggest that tunable orientational nonlinearity of nematic liquid crystals can be employed for all-optical switching in periodic photonic structures with liquid-crystal defects. We consider a one-dimensional periodic structure of Si layers with a local defect created by infiltrating a liquid crystal into a pore, and demonstrate, by solving numerically a system of coupled nonlinear equations for the nematic director and the propagating electric field, that the light-induced Freedericksz transition can lead to a sharp switching and diode operation in the photonic devices.
TL;DR: All-optical beam steering in modulated photonic lattices induced optically by three-beam interference in a biased photorefractive crystal is demonstrated and it is shown that the spatial resolution can be enhanced by the additional effect of nonlinear beam self-localization.
Abstract: We demonstrate experimentally all-optical beam steering in modulated photonic lattices induced optically by three-beam interference in a biased photorefractive crystal. We identify and characterize the key physical parameters governing the beam steering and show that the spatial resolution can be enhanced by the additional effect of nonlinear beam self-localization.
TL;DR: The phase coherence and the effect of quantum fluctuations on q vortices are examined and it is revealed that the breakdown of these coherent structures through quantum fluctuations accompanies the superfluid-insulator crossover.
Abstract: We consider nonlinear boson states with a nontrivial phase structure in the three-site Bose-Hubbard ring, quantum discrete vortices (or $q$ vortices), and study their ``melting'' under the action of quantum fluctuations. We calculate the spatial correlations in the ground states to show the superfluid-insulator crossover and analyze the fidelity between the exact and variational ground states to explore the validity of the classical analysis. We examine the phase coherence and the effect of quantum fluctuations on $q$ vortices and reveal that the breakdown of these coherent structures through quantum fluctuations accompanies the superfluid-insulator crossover.
TL;DR: In this article, the authors describe the physics of nonlinear magnetoinductive waves in left-handed composite metamaterials and derive the coupled equations for describing the propagation of magneto-inductive wave, and show that in the nonlinear regime the magnetic response of a metammaterial may become bistable.
Abstract: We describe novel physics of nonlinear magnetoinductive waves in left-handed composite metamaterials. We derive the coupled equations for describing the propagation of magnetoinductive waves, and show that in the nonlinear regime the magnetic response of a metamaterial may become bistable. We analyze modulational instability of different nonlinear states, and also demonstrate that nonlinear metamaterials may support the propagation of domain walls (kinks) connecting the regions with the positive and negative magnetization.
TL;DR: This work finds numerically discrete surface modes in semi-infinite binary waveguide arrays which can support simultaneously two types of discrete solitons, and analyzes different multi-gap states including the soliton-induced waveguides with the guided modes from different gaps and composite vector solitONS.
Abstract: We analyze nonlinear collective effects near surfaces of semi-infinite periodic systems with multi-gap transmission spectra and introduce a novel concept of multi-gap surface solitons as mutually trapped surface states with the components associated with different spectral gaps. We find numerically discrete surface modes in semi-infinite binary waveguide arrays which can support simultaneously two types of discrete solitons, and analyze different multi-gap states including the soliton-induced waveguides with the guided modes from different gaps and composite vector solitons.
TL;DR: The results suggest opportunities for efficient self-collimation, focusing, and reshaping of beams produced by white-light and supercontinuum sources and predict a possibility of multicolor Talbot effect, which is not possible in free space or conventional photonic lattices.
Abstract: We introduce periodic photonic structures where the strength of diffraction can be managed in a very broad frequency range. We show how to design arrays of curved waveguides where light beams experience wavelength-independent normal, anomalous, or zero diffraction. Our results suggest opportunities for efficient self-collimation, focusing, and reshaping of beams produced by white-light and supercontinuum sources. We also predict a possibility of multicolor Talbot effect, which is not possible in free space or conventional photonic lattices.
TL;DR: In this article, double-resonant (binary) metamaterials composed of two types of magnetic resonant elements are proposed for phase-matched parametric interaction and enhanced second-harmonic generation.
Abstract: We suggest double-resonant (binary) metamaterials composed of two types of magnetic resonant elements, and demonstrate that in the nonlinear regime such metamaterials provide unique possibilities for phase-matched parametric interaction and enhanced second-harmonic generation.
TL;DR: For the first time, the nontrivial topological transformations of the discrete vortex including the flipping of vortex charge and inversion of its orbital angular momentum are described theoretically and observed in experiment.
Abstract: We study interaction of a discrete vortex with a supporting photonic lattice and analyze how the combined action of the lattice periodicity and the medium nonlinearity can modify the vortex structure. In particular, we describe theoretically and observe in experiment, for the first time to our knowledge, the nontrivial topological transformations of the discrete vortex including the flipping of vortex charge and inversion of its orbital angular momentum. We also demonstrate the stabilizing effect of the interaction with the so-called “mixed” optically-induced photonic lattices on the vortex propagation and topological structure.
TL;DR: The experimental observation of self-trapping and nonlinear localization of light in such segmented lattices in the form of ring-shaped and single-site states agrees well with numerical simulations accounting for an anisotropic and spatially nonlocal nonlinear response of photorefractive crystals.
Abstract: We generate higher-order azimuthally modulated Bessel optical lattices in photorefractive crystals by employing a phase-imprinting technique. We report on the experimental observation of self-trapping and nonlinear localization of light in such segmented lattices in the form of ring-shaped and single-site states. The experimental results agree well with numerical simulations accounting for an anisotropic and spatially nonlocal nonlinear response of photorefractive crystals.
TL;DR: In this paper, different types of two-dimensional Bloch waves of a square photonic lattice were generated experimentally by employing the phase imprinting technique, and the local dispersion of the Bloch modes was investigated by analyzing the linear diffraction of beams associated with the high symmetry points of the Brillouin zone, and also distinguish the regimes of normal, anomalous and anisotropic diffraction through observations of nonlinear self-action effects.
Abstract: We generate experimentally different types of two-dimensional Bloch waves of a square photonic lattice by employing the phase imprinting technique. We probe the local dispersion of the Bloch modes in the photonic lattice by analyzing the linear diffraction of beams associated with the high-symmetry points of the Brillouin zone, and also distinguish the regimes of normal, anomalous, and anisotropic diffraction through observations of nonlinear self-action effects.
TL;DR: It is demonstrated that propagation direction and velocity of optical pulses can be controlled independently in the structures with multiscale modulation of the refractive index in transverse and longitudinal directions, and the possibility for self-collimation of slow light when spatial diffraction is suppressed for certain propagation directions is identified.
Abstract: We demonstrate that propagation direction and velocity of optical pulses can be controlled independently in the structures with multiscale modulation of the refractive index in transverse and longitudinal directions. We reveal that, in arrays of waveguides with phase-shifted Bragg gratings, the refraction angle does not depend on the speed of light, allowing for efficient spatial steering of slow light. In this system, both spatial diffraction and temporal dispersion can be designed independently, and we identify the possibility for self-collimation of slow light when spatial diffraction is suppressed for certain propagation directions. We also show that broadening of pulses in space and time can be eliminated in nonlinear media, supporting the formation of slow-light optical bullets that remain localized irrespective of propagation direction.