Guiding light at the nanoscale: numerical optimization of ultrasubwavelength metallic wire plasmonic waveguides

We present a comprehensive numerical analysis of the guiding of a photonic signal in the form of a strongly confined asymmetric surface plasmon polariton (SPP) mode along metallic nanowire waveguides. The proposed approach provides extremely high localization of the SPP mode, nanoscale integration density, and a feasible technological platform. The waveguide performance was studied over a broad range of subwavelength cross sections at a telecommunication wavelength. It was optimized using a conventional figure of merit for data transfer along a straight waveguide and an all-inclusive figure of merit has been introduced.     

Brillouin scattering of light by spin waves in ferromagnetic nanorods

We report the investigations of spin wave modes of arrays of Ni and Co nanorods using Brillouin light scattering. We have revealed the significant influence of spin wave modes along the nanorod axis in contrast to infinite magnetic nanowires. Unusual optical properties featuring an inverted Stokes/anti-Stokes asymmetry of the Brillouin scattering spectra have been observed. The spectrum of spin wave modes in the nanorod array has been calculated and compared with the experiment. Experimental observations are explained in terms of a combined numerical–analytical approach taking into account both the low aspect ratio of individual magnetic nanorods and dipolar magnetic coupling between the nanorods in the array. The optical studies of spin-wave modes in nanorod metamaterials with low aspect ratio nanorods have revealed new magnetic and magneto-optical properties compared to continuous magnetic films or infinite magnetic nanowires. Such magnetic artificial materials are important class of active metamaterials needed for prospective data storage and signal processing applications.     

On the Choice of the Wavefunction of the Ground State of He for Precision Calculations of Autoionization State Parameters above the Excited Ion Formation Threshold

The necessity of choosing multiparametric wavefunctions for describing the ground state of an atom in the problems of ionization of atoms by photons and electrons has been substantiated for the He atom as an example. Comparative analysis of application of different ground-state wavefunctions for this atom has been performed. The energies, widths, and partial widths of the lower autoionization state ¹P of the He atom above the excited ion formation threshold has been performed. It is shown that in contrast to total widths of quasi-stationary states, which differ insignificantly for different wavefunctions of the ground state, the partial widths are substantially different.     

Dispersing light with surface plasmon polaritonic crystals

Spectral dispersion of light on a finite-size surface plasmon polaritonic (SPP) crystal has been studied. The angular wavelength separation of one or more orders of magnitude higher than in other state-of-the-art wavelength-splitting devices available to date has been demonstrated. The two-stage process is responsible for the dispersion value, which involves conversion of the incident light into SPP Bloch modes of a nanostructure followed by the SPP Bloch waves refraction at the SPP crystal boundary. The high spectral dispersion achievable in plasmonic devices may be useful for integrated high-resolution spectroscopy in nanophotonic, optical communication and lab-on-a-chip applications.     

Influence of substituents in pyrrole rings on electronic structure and molecular electrostatic potentials of porphyrins

The distributions of the molecular electrostatic potential in the central cavities of the free bases protoporphyrin IX, mesoporphyrin IX, etioporphyrin III and of their mono- and dianions have been calculated. An analysis has been made of the influence of substituents in the pyrrole rings of the investigated porphyrins on the potential distribution in their central cavities and the possible mechanism for addition of protons to the appropriate dianions.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 24, No. 3, pp. 335–339, May–June, 1988.     

Reconstitution of apo-glucose dehydrogenase on pyrroloquinoline quinone-functionalized au nanoparticles yields an electrically contacted biocatalyst

An electrically contacted glucose dehydrogenase (GDH) enzyme electrode is fabricated by the reconstitution of the apo-GDH on pyrroloquinoline quinone (PQQ)-functionalized Au nanoparticles (Au-NPs), 1.4 nm, associated with a Au electrode. The Au-NPs functionalized with a single amine group were attached to the Au surface by 1,4-benzenedithiol bridges, and PQQ was covalently linked to the Au-NPs. The apo-GDH was then reconstituted on the PQQ cofactor sites. The surface coverage of GDH corresponded to 1.4 x 10(-12) mol cm(-2). The reconstituted enzyme revealed direct electrical contact with the electrode surface, and the bioelectrocatalytic oxidation of glucose occurred with a turnover number of 11,800 s(-1). In contrast, a system that included the covalent attachment of GDH to the PQQ-Au-NPs monolayer in a random, nonaligned, configuration revealed lack of electrical communication between the enzyme and the electrode, albeit the enzyme existed in a bioactive structure. The bioelectrocatalytic function of the later system was, however, activated by the diffusional electron mediator 2,6-dichlorophenol-indophenol. The results imply that the alignment of GDH on a Au-NP through the reconstitution process leads to an electrically contacted enzyme-electrode, where the Au-NP acts as a charge-transfer mediator.     

The effect of the surface enhanced polariton field on the tunneling current of a STM

The influence of surface polaritons (SPs), excited on the external (fast mode) and internal (slow mode) surfaces of a gold film, on the tunneling current of a STM is investigated. The role of the surface polaritons is directly demonstrated by the angular excitation spectra of the induced tunneling current. Possible mechanisms which might give rise to the SP induced change in the tunneling current are discussed. An electromagnetic field of SPs within a tunneling gap is estimated to be surface enhanced in order to explain the value of the induced tunneling current. Images of the polariton induced signal distribution over the sample surface taken by means of different SP modes are compared in order to obtain information on the structure of the internal surface of the film.     

Nonlinear surface plasmon polaritonic crystals

We present an overview of the optical properties of nonlinear surface plasmon polaritonic crystals and their applications to control light with light. Surface plasmon polaritonic crystals are periodically nanostructured metal surfaces or thin metal films that act as two‐dimensional photonic crystals for surface polaritons. Hybritization of such nanostructures with dielectrics exhibiting an optical nonlinear response allows utilization of the electromagnetic field enhancement effects to observe nonlinear effects and bistable behaviour at low light intensities. By changing the geometry of the nanostructured film, the dispersion of the crystal is modified and, thus, electromagnetic mode structure and associated density of states can be controllably tuned in the desired spectral range. This provides enhanced flexibility in engineering the nonlinear optical response of plasmonic crystals in a chosen spectral range for both control and signal wavelengths.