Anna S. Zelenina

Enhanced optical forces between coupled resonant metal nanoparticles

We investigate numerically the optical forces between noble metal nanoparticles sustaining localized surface plasmon resonances. Our results first point out enhanced binding optical forces compared with dielectric nanoparticles and nonresonant metallic nanoparticles. We also show that under suitable illumination conditions, short-range forces tend to make the nanoparticles cluster, leading to intense and localized hot spots in the interstices. This effect corroborates recent experimental observations of an enhanced Raman signal in trapped metal sphere ensembles.

Spatial soliton switching in quasi-continuous optical arrays

We report on the phenomenon of trapping and switching of one-dimensional spatial solitons in Kerr-type nonlinear media with transverse periodic modulation of the refractive index. The solitons slowly radiate upon propagation along the periodic structure and are finally trapped in one of its guiding channels. The position of the output channel can be varied by small changes in the launching angle.

Tunable optical sorting and manipulation of nanoparticles via plasmon excitation

We numerically investigate the optical forces exerted by an incident light beam on Rayleigh metallic particles over a dielectric substrate. In analogy with atom manipulation, we identify two different trapping regimes depending on whether the illumination is performed within the plasmon band or out of it. By adjusting the incident wavelength, the particles can be selectively guided, or immobilized, at the substrate interface.

Soliton Eigenvalue Control in Optical Lattices

We address the dynamics of higher-order solitons in optical lattices, and predict their self-splitting into the set of their single-soliton constituents. The splitting is induced by the potential introduced by the lattice, together with the imprinting of a phase tilt onto the initial multisoliton states. The phenomenon allows the controllable generation of several coherent solitons linked via their Zakharov-Shabat eigenvalues. Application of the scheme to the generation of correlated matter waves in Bose-Einstein condensates is discussed.

Eigenvalue control and switching by fission of multisoliton bound states in planar waveguides

We report the results of numerical studies of the fission of N-soliton bound states at the interface formed by a Kerr nonlinear medium and a linear dielectric in a planar waveguide. A variety of effects are shown to occur, with applications to all-optical eigenvalue soliton control.

Stabilization of vector solitons in optical lattices

We address the properties and dynamical stability of one-dimensional vector lattice solitons in a Kerr-type cubic medium with harmonic transverse modulation of the refractive index. We discovered that unstable families of scalar lattice solitons can be stabilized via cross-phase modulation (XPM) in the vector case. It was found that multihumped vector solitons that are unstable in uniform media where the XPM strength is higher than that of self-phase modulation can also be stabilized by the lattice.

Stable multicolor periodic-wave arrays

We study the existence and stability of periodic-wave arrays propagating in uniform quadratic nonlinear media and discover that they become completely stable above a threshold light intensity. To the best of our knowledge, this is the first example in physics of completely stable periodic-wave patterns propagating in conservative uniform media supporting bright solitons.

Transverse modulational instability of (2 + 1)-dimensional cnoidal waves in media with cubic nonlinearity

We consider transverse modulational instability of (2+1)-dimensional cnoidal waves of cn, dn, and sn, types that are periodic in one direction and are uniform in the other direction. The new method of stability analysis of periodic waves presented here is based on the construction of a translation matrix for a perturbation vector and on the evolution of the eigenvalues of the matrix with changes in modulation frequency and Jacobi parameter that define the degree of energy localization of the corresponding cnoidal waves. We show that the dn wave is subject to the influence of both neck and snake instabilities, the cn wave is affected by neck instability, and the sn wave suffers from snake instability in (2+1) dimensions.

Parallel and selective trapping in a patterned plasmonic landscape

The implementation of optical tweezers at a surface opens a huge potential towards the elaboration of future lab-on-a-chip devices entirely operated with light. The transition from conventional three-dimensional (3D) tweezers to 2D is made possible by exploiting evanescent fields bound at interfaces. In particular, surface plasmons (SP) at metal/dielectric interfaces are expected to be excellent candidates to relax the requirements on incident power and to achieve subwavelength trapping volumes. Here, we report on novel 2D SP-based optical tweezers formed by finite gold areas fabricated at a glass surface. We demonstrate that SP enable stable trapping of single dielectric beads under unfocused illumination with considerably reduced laser intensity compared with conventional optical tweezers. We show that the method can be extended to parallel trapping over any predefined pattern. Finally, we demonstrate how SP tweezers can be designed to selectively trap one type of particles out of a mixture, acting as an efficient optical sieve.

Multiple trapping in a patterned plasmonic landscape

We report on a novel optical manipulation method based on a transparent surface patterned with metal microstructures supporting surface plasmon (SP). Such SP-tweezers enable from a single light beam to arrange according to any predefined pattern many micro-objects on a surface.