622 research outputs found
Localization of Surface Plasmon Polaritons in Hexagonal Arrays of Moire Cavities
Cataloged from PDF version of article.In view of the progress on the confinement of light, we report on the dispersion characteristics of surface plasmon polaritons (SPPs) on two-dimensional Moire surfaces in the visible part of the electromagnetic spectrum. Polarization dependent spectroscopic reflection measurements show omnidirectional confinement of SPPs. The resonance wavelength of SPP cavity modes can be adjusted by tuning the propagation direction of SPPs. The results may have an impact on the control of spontaneous emission and absorption with applications in light emitting diodes and solar cells, as well as in quantum electrodynamics experiments. (C) 2011 American Institute of Physics. [doi:10.1063/1.3529469
An elastomeric grating coupler
We report on a novel nondestructive and reversible method for coupling free space light to planar optical waveguides. In this method, an elastomeric grating is used to produce an effective refractive index modulation on the surface of the optical waveguide. The external elastomeric grating binds to
the surface of the waveguide with van der Waals forces and makes conformal contact without any applied pressure. As a demonstration of the feasibility of the approach, we use it to measure the refractive index of a silicon oxynitride film. This technique is nondestructive, reversible, low cost
and can easily be applied to the characterization of optical materials for integrated optics
Slowing surface plasmon polaritons on plasmonic coupled cavities by tuning grating grooves
Cataloged from PDF version of article.We investigate slow surface plasmon polaritons (SPPs) in plasmonic waveguiding bands formed by coupled plasmonic cavities on Moire surfaces. We demonstrate controlling the group velocity and dispersion of the SPPs by varying the depth of the plasmonic Bragg grating groove. Changing the grating depth results in modification of coupling coefficients between the cavities and hence the SPPs group velocity is altered. Variation in the group velocity and dispersion of SPPs can be measured with polarization dependent spectroscopic reflection measurements. Dispersion of SPPs has been calculated by finite-difference time-domain method in agreement with the experimental data. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3495781
Binary Sequences With Low Aperiodic Autocorrelation for Synchronization Purposes
Cataloged from PDF version of article.An evolutionary algorithm is used to find three sets
of binary sequences of length 49–100 suitable for the synchronization
of digital communication systems. Optimization of the sets are
done by taking into consideration the type of preamble used in
data frames and the phase-lock mechanism of the communication
system. The preamble is assumed to be either a pseudonoise (PN)
sequence or a sequence of 1’s. There may or may not be phase ambiguity
in detection. With this categorization, the first set of binary
sequences is optimized with respect to aperiodic autocorrelation
which corresponds to the random (PN) preamble without phase
ambiguity case. The second and third sets are optimized with respect
to a modified aperiodic autocorrelation for different figures
of merit corresponding to the predetermined preamble (sequence
of 1’s) with and without phase ambiguity cases
Grating based plasmonic band gap cavities
Cataloged from PDF version of article.We report on a comparative study of grating based plasmonic band gap cavities. Numerically, we calculate the quality factors of the cavities based on three types of grating surfaces; uniform, biharmonic and Moiré surfaces. We show that for biharmonic band gap cavities, the radiation loss can be suppressed by removing the additional grating component in the cavity region. Due to the gradual change of the surface profile in the cavity region, Moiré type surfaces support cavity modes with higher quality factors. Experimentally, we demonstrate the existence of plasmonic cavities based on uniform gratings. Effective index perturbation and cavity geometries are obtained by additional dielectric loading. Quality factor of 85 is obtained from the measured band structure of the cavity. © 2009 Optical Society of America
Critical coupling in plasmonic resonator arrays
Cataloged from PDF version of article.We report critical coupling of electromagnetic waves to plasmonic cavity arrays fabricated on Moire surfaces. Dark field plasmon microscopy imaging and polarization dependent spectroscopic reflection measurements reveal the critical coupling conditions of the cavities. The critical coupling conditions depend on the superperiod of the Moire surface, which also defines the coupling between the cavities. Complete transfer of the incident power can be achieved for traveling wave plasmonic resonators, which have a relatively short superperiod. When the superperiod of the resonators increases, the coupled resonators become isolated standing wave resonators in which complete transfer of the incident power is not possible. Analytical and finite difference time domain calculations support the experimental observations. (C) 2011 Optical Society of Americ
Topological transitions in carbon nanotube networks via nanoscale confinement
Efforts aimed at large-scale integration of nanoelectronic devices that
exploit the superior electronic and mechanical properties of single-walled
carbon nanotubes (SWCNTs) remain limited by the difficulties associated with
manipulation and packaging of individual SWNTs. Alternative approaches based on
ultra-thin carbon nanotube networks (CNNs) have enjoyed success of late with
the realization of several scalable device applications. However, precise
control over the network electronic transport is challenging due to i) an often
uncontrollable interplay between network coverage and its topology and ii) the
inherent electrical heterogeneity of the constituent SWNTs. In this letter, we
use template-assisted fluidic assembly of SWCNT networks to explore the effect
of geometric confinement on the network topology. Heterogeneous SWCNT networks
dip-coated onto sub-micron wide ultra-thin polymer channels exhibit a topology
that becomes increasingly aligned with decreasing channel width and thickness.
Experimental scale coarse-grained computations of interacting SWCNTs show that
the effect is a reflection of an aligned topology that is no longer dependent
on the network density, which in turn emerges as a robust knob that can induce
semiconductor-to-metallic transitions in the network response. Our study
demonstrates the effectiveness of directed assembly on channels with varying
degrees of confinement as a simple tool to tailor the conductance of the
otherwise heterogeneous network, opening up the possibility of robust
large-scale CNN-based devices.Comment: 4 pages, 3 figure
Absorption enhancement of molecules in the weak plasmon-exciton coupling regime
Cataloged from PDF version of article.We report on the experimental and theoretical investigations of enhancing the optical absorption of organic molecules
in the weak plasmon–exciton coupling regime. A metal–organic hybrid structure consisting of dye molecules
embedded in the polymer matrix is placed in close vicinity to thin metal films. We have observed a transition from a
weak coupling regime to a strong coupling one as the thickness of the metal layer increases. The results indicate that
absorption of the self-assembled J-aggregate nanostructures can be increased in the weak plasmon–exciton coupling
regime and strongly quenched in the strong coupling regime. A theoretical model based on the transfer-matrix
method qualitatively confirms the experimental results obtained from polarization-dependent spectroscopic
reflection measurements
Plexcitonic crystals: a tunable platform for light-matter interactions
Cataloged from PDF version of article.Coupled states of surface plasmon polaritons (SPPs) and excitons are collectively called plexcitons [Nano Lett. 8, 3481 (2008)]. Plexcitonics is an emerging field of research aiming to control light-matter interaction at the nanometer length scale using coupled pairs of surface-plasmons and excitons. Ability to control the interaction between localized excitons and propagating surface-plasmons is important for realization of new photonic devices. In this letter, we report plexcitonic crystals that yield direction-dependent plasmon-exciton coupling. We have fabricated one- and two-dimensional plexcitonic crystals on periodically corrugated silver surfaces, which are loaded with J-aggregate complexes. We show that plasmon-exciton coupling is blocked for some crystal directions when exciton energy falls inside the plasmonic band gap of the periodically corrugated metallic surface. (C) 2014 Optical Society of Americ
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