22,765 research outputs found
Boundary effects in finite size plasmonic crystals: Focusing and routing of plasmonic beams for optical communications
Plasmonic crystals, which consist of periodic arrangements of surface features at a metal-dielectric interface, allow the manipulation of optical information in the form of surface plasmon polaritons. Here we investigate the excitation and propagation of plasmonic beams in and around finite size plasmonic crystals at telecom wavelengths, highlighting the effects of the crystal boundary shape and illumination conditions. Significant differences in broad plasmonic beam generation by crystals of different shapes are demonstrated, while for narrow beams, the propagation onto the smooth metal film is less sensitive to the crystal boundary shape. We show that by controlling the boundary shape, the size and the excitation beam parameters, directional control of propagating plasmonic modes and associated beam parameters such as angular beam splitting, focusing power and beam width can be efficiently achieved. This provides a promising route for robust and alignment-independent integration of plasmonic crystals with optical communication components
Scattering-free plasmonic optics with anisotropic metamaterials
We develop an approach to utilize anisotropic metamaterials to solve one of
the fundamental problems of modern plasmonics -- parasitic scattering of
surface waves into free-space modes, opening the road to truly two-dimensional
plasmonic optics. We illustrate the developed formalism on examples of
plasmonic refractor and plasmonic crystal, and discuss limitations of the
developed technique and its possible applications for sensing and imaging
structures, high-performance mode couplers, optical cloaking structures, and
dynamically reconfigurable electro-plasmonic circuits
Tuning and Switching a Plasmonic Quantum Dot Sandwich in a Nematic Line Defect
We study the quantum-mechanical effects arising in a single semiconductor
core/shell quantum dot controllably sandwiched between two plasmonic nanorods.
Control over the position and the sandwich confinement structure is achieved by
the use of a linear-trap, liquid-crystal line defect and laser tweezers that
push the sandwich together. This arrangement allows for the study of exciton
plasmon interactions in a single structure, unaltered by ensemble effects or
the complexity of dielectric interfaces. We demonstrate the effect of plasmonic
confinement on the photon-antibunching behavior of the quantum dot and its
luminescence lifetime. The quantum dot behaves as a single emitter when
nanorods are far away from the quantum dot but shows possible multiexciton
emission and a significantly decreased lifetime when tightly confined in a
plasmonic sandwich. These findings demonstrate that liquid crystal defects,
combined with laser tweezers, enable a versatile platform to study plasmonic
coupling phenomena in a nanoscale laboratory, where all elements can be
arranged almost at will.Comment: Supporting information at the en
Complex k band diagrams of 3D metamaterial/photonic crystals
A finite element method (FEM) for solving the complex valued k({\omega}) vs.
{\omega} dispersion curve of a 3D metamaterial/photonic crystal system is
presented. This 3D method is a generalization of a previously reported 2D
eigenvalue method. This method is particularly convenient for analyzing
periodic systems containing dispersive (e.g., plasmonic) materials, for
computing isofrequency surfaces in the k-space, and for calculating the decay
length of the evanescent waves. Two specific examples are considered: a
photonic crystal comprised of dielectric spheres and a plasmonic fishnet
structure. Hybridization and avoided crossings between Mie resonances and
propagating modes are numerically demonstrated. Negative index propagation of
four electromagnetic modes distinguished by their symmetry is predicted for the
plasmonic fishnets. By calculating the isofrequency contours, we also
demonstrate that the fishnet structure is a hyperbolic medium
Noncentrosymmetric plasmon modes and giant terahertz photocurrent in a two-dimensional plasmonic crystal
We introduce and theoretically study the plasmon-photogalvanic effect in the
planar noncentrosymmetric plasmonic crystal containing a homogeneous
two-dimensional electron system gated by a periodic metal grating with an
asymmetric unit cell. The plasmon-photogalvanic DC current arises due to the
two-dimensional electron drag by the noncentrosymmetric plasmon modes excited
under normal incidence of terahertz radiation. We show that the collective
plasmon modes of the planar plasmonic crystal become strongly
noncentrosymmetric in the weak coupling regime of their anticrossing. Large
plasmon wavevector (which is typically by two-three orders of magnitude greater
than the terahertz photon wavevector) along with strong near-field enhancement
at the plasmon resonance make the plasmonic drag a much stronger effect
compared to the photon drag observed in conventional two-dimensional electron
systems.Comment: 9 pages, 10 figures, submitted to Physical Review
Shaping plasmon beams via the controlled illumination of finite-size plasmonic crystals
Plasmonic crystals provide many passive and active optical functionalities, including enhanced sensing, optical nonlinearities, light extraction from LEDs and coupling to and from subwavelength waveguides. Here we study, both experimentally and numerically, the coherent control of SPP beam excitation in finite size plasmonic crystals under focussed illumination. The correct combination of the illuminating spot size, its position relative to the plasmonic crystal, wavelength and polarisation enables the efficient shaping and directionality of SPP beam launching. We show that under strongly focussed illumination, the illuminated part of the crystal acts as an antenna, launching surface plasmon waves which are subsequently filtered by the surrounding periodic lattice. Changing the illumination conditions provides rich opportunities to engineer the SPP emission pattern. This offers an alternative technique to actively modulate and control plasmonic signals, either via micro- and nano-electromechanical switches or with electro- and all-optical beam steering which have direct implications for the development of new integrated nanophotonic devices, such as plasmonic couplers and switches and on-chip signal demultiplexing. This approach can be generalised to all kinds of surface waves, either for the coupling and discrimination of light in planar dielectric waveguides or the generation and control of non-diffractive SPP beams
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