Maxim Sukharev

Strong coupling between molecular excited states and surface plasmon modes of a slit array in a thin metal film

A recent study of the Seideman group with international collaborators, unravels a new and fascinating phenomenon in strongly coupled molecules-nanoconstruct systems, namely, the emergence of a new spectral mode associated with collective, plasmon-induced interaction among the molecules. Ongoing work explores applications of the unique properties of the discovered mode, ranging from solar energy conversion to plasmon-enhanced spectroscopies and sensing. Transmission spectra illustrating the emergence of a new, nondispersive mode. The inset gives the transmission vs the distance of the molecules from the plasmonic array.

Transport and optical response of molecular junctions driven by surface plasmon polaritons

We consider a biased molecular junction subjected to external time-dependent electromagnetic field. The field for two typical junction geometries (bowtie antennas and metal nanospheres) is calculated within finite-difference time-domain technique. Time-dependent transport and optical response of the junctions is calculated within nonequilibrium Greens-function approach expressed in a form convenient for description of multilevel systems. We present numerical results for a two-level (highest occupied molecular orbital-lowest unoccupied molecular orbital) model and discuss influence of localized surface plasmon-polariton modes on transport.

Coherent control approaches to light guidance in the nanoscale

Concepts of coherent control are extended to manipulate light in subdiffraction length scales via nanoparticle arrays. Phase and polarization control are first introduced and applied to control the pathway of electromagnetic energy through multiple branching nanoarray intersections, leading to an ultrafast optical nanoswitch below the diffraction limit. The genetic algorithm is next generalized to provide a systematic design tool, wherein both the properties of the excitation field and the structural parameters of the material system are optimized so as to make nanodevices with desired functionality. The scheme is used to gain insight into the interplay between the interactions that underlies the coherent propagation of electromagnetic energy via nanoparticle arrays. Implications to several research fields, including single molecule spectroscopy, spatially confined chemistry, optical logic, and nanoscale sensing, are envisioned.

Numerical studies of the interaction of an atomic sample with the electromagnetic field in two dimensions

We consider the interaction of electromagnetic radiation of arbitrary polarization with multilevel atoms in a self-consistent manner, taking into account both spatial and temporal dependencies of localfields. This is done by numerically solvingthe corresponding systemofcoupled Maxwell-Liouville equations forvarious geometries. In particular, we scrutinize linear optical properties of nanoscale atomic clusters, demonstrating the significant role played by collective effects and dephasing. It is shown that subwavelength atomic clusters exhibit two resonant modes, one of which is localized slightly below the atomic transition frequency of an individual atom, while the other is positioned considerably above it. As an initial exploration of future applications of this approach, the optical response of core-shell nanostructures, with a core consisting of silver and a shell composed of resonant atoms, is examined.

Coherent control of light propagation via nanoparticle arrays

We illustrate the possibility of manipulating light in the nanoscale using the combination of plasmonics physics with concepts and tools developed for coherent control of molecular dynamics. Phase and polarization control are applied to guide electromagnetic energy through metal nanoparticle junctions and control its branching ratios at array intersections. Optimal control theory is applied as a design tool, to develop constructs with desired functionality. We suggest also that nanoplasmonics could be used to make spatially localized light sources with predesigned coherence and polarization properties, which could serve to coherently control individual nano-systems.

Light-induced current in molecular junctions: Local field and non-Markov effects

We consider a two-level system coupled to contacts as a model for charge pump under external laser pulse. The model represents a charge-transfer molecule in a junction, and is a generalization of previously published results [B. D. Fainberg, M. Jouravlev, and A. Nitzan. Phys. Rev. B 76, 245329 (2007)]. Effects of local field for realistic junction geometry and non-Markov response of the molecule are taken into account within finite-difference time-domain (FDTD) and on-the-contour equation-of-motion (EOM) formulations, respectively. Our numerical simulations are compared to previously published results.

Ultrafast Energy Transfer between Molecular Assemblies and Surface Plasmons in the Strong Coupling Regime

The nonlinear optical dynamics of nanomaterials comprised of plasmons interacting with quantum emitters is investigated by a self-consistent model based on the coupled Maxwell-Liouville-von Neumann equations. It is shown that ultrashort resonant laser pulses significantly modify the optical properties of such hybrid systems. It is further demonstrated that the energy transfer between interacting molecules and plasmons occurs on a femtosecond time scale and can be controlled with both material and laser parameters.

Optical properties of metal tips for tip-enhanced spectroscopies

We develop a full 3D approach to simulate the optical properties of sharp metal tips that could be quantitatively compared with experiments and provide accurate predictions. Similar to metallic wires, elongated metal tips support a series of extended mode resonances whose properties are largely determined by the tip geometry and are essentially independent of the tip material. For sufficiently long tips, these resonances are energetically well separated from a broader, high-energy feature, whose position and line shape are independent of the tip length but vary strongly with the tip material. The latter is a localized plasmon mode characterized by the hemisphere terminating the tip.

Surface quality and surface waves on subwavelength-structured silver films

Using transmission electron microscopy (TEM) to analyse the physical-chemical surface properties of subwavlength structured silver films and finite-difference time-domain (FDTD) numerical simulations of the optical response of these structures to plane-wave excitation, we report on the origin and nature of the persistent surface waves generated by a single slit-groove motif and recently measured by far-field optical interferometry. The surface analysis shows that the silver films are free of detectable oxide or sulfide contaminants, and the numerical simulations show very good agreement with the results previously reported.

Optical properties of metal nanoparticles with no center of inversion symmetry: Observation of volume plasmons

We present theoretical and experimental studies of the optical response of L-shaped silver nanoparticles. The scattering spectrum exhibits several plasmon resonances that depend sensitively on the polarization of the incident electromagnetic field. The physical origin of the resonances is traced to different plasmon phenomena. In particular, a high energy band with unusual properties is interpreted in terms of volume plasmon oscillations arising from the asymmetry of a nanoparticle.