1,030 research outputs found
Second-harmonic generation in subwavelength graphene waveguides
We suggest a novel approach for generating second-harmonic radiation in
subwavelength graphene waveguides. We demonstrate that quadratic phase matching
between the plasmonic guided modes of different symmetries can be achieved in a
planar double-layer geometry when conductivity of one of the layers becomes
spatially modulated. We predict theoretically that, owing to graphene nonlocal
conductivity, the second-order nonlinear processes can be actualized for
interacting plasmonic modes with an effective grating coupler to allow external
pumping of the structure and output of the radiation at the double frequency.Comment: 5 pages, 3 figure
Necklace-ring vector solitons
We introduce novel classes of optical vector solitons that consist of incoherently coupled self-trapped “necklace” beams carrying zero, integer, and even fractional angular momentum. Because of the stabilizing mutual attraction between the components, such stationary localized structures exhibit quasistable propagation for much larger distances than the corresponding scalar vortex solitons and expanding scalar necklace beams
Broadband light coupling to dielectric slot waveguides with tapered plasmonic nanoantennas
We propose and theoretically verify an efficient mechanism of broadband
coupling between incident light and on-chip dielectric slot waveguide by
employing a tapered plasmonic nanoantenna. Nanoantenna receives free space
radiation and couples it to a dielectric slot waveguide with the efficiency of
up to 20% in a broad spectral range, having a small footprint as compared with
the currently used narrowband dielectric grating couplers. We argue that the
frequency selective properties of such nanoantennas also allow for using them
as ultrasmall on-chip multiplexer/demultiplexer devices
Localization of Two-Component Bose-Einstein Condensates in Optical Lattices
We reveal underlying principles of nonlinear localization of a two-component
Bose-Einstein condensate loaded into a one-dimensional optical lattice. Our
theory shows that spin-dependent optical lattices can be used to manipulate
both the type and magnitude of nonlinear interaction between the ultracold
atomic species and to observe nontrivial two-componentnlocalized states of a
condensate in both bands and gaps of the matter-wave band-gap structure.Comment: 4 pages, 4 figure
Beaming effect from increased-index photonic crystal waveguides
We study the beaming effect of light for the case of increased-index photonic
crystal (PhC) waveguides, formed through the omission of low-dielectric media
in the waveguide region. We employ the finite-difference time-domain numerical
method for characterizing the beaming effect and determining the mechanisms of
loss and the overall efficiency of the directional emission. We find that,
while this type of PhC waveguides is capable of producing a highly collimated
emission as was demonstrated experimentally, the inherent characteristics of
the structure result in a restrictively low efficiency in the coupling of light
into the collimated beam of light.Comment: 4 pages, 5 figures, submitted to Applied Physics
Multi-gap discrete vector solitons
We analyze nonlinear collective effects in periodic systems with multi-gap
transmission spectra such as light in waveguide arrays or Bose-Einstein
condensates in optical lattices. We demonstrate that the inter-band
interactions in nonlinear periodic gratings can be efficiently managed by
controlling their geometry, and predict novel types of discrete vector solitons
supported by nonlinear coupling between different bandgaps and study their
stability.Comment: 4 pages, 4 figure
Single- and double-vortex vector solitons in self-focusing nonlinear media
We study two-component spatial optical solitons carrying an angular momentum
and propagating in a self-focusing saturable nonlinear medium. When one of the
components is small, such vector solitons can be viewed as a self-trapped
vortex beam that guides either the fundamental or first-order guided mode, and
they are classified as single- and double-vortex vector solitons. For such
composite vortex beams, we demonstrate that a large-amplitude guided mode can
stabilize the ring-like vortex beam which usually decays due to azimuthal
modulational instability. We identify different types of these vector vortex
solitons and demonstrate both vortex bistability and mutual stabilization
effect.Comment: 7 pages, 13 figure
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