447 research outputs found
Tapered Yagi-Uda Nanoantennas for Broadband Unidirectional Emission
We demonstrate experimentally the operation of tapered Yagi-Uda nanoantennas
for broadband unidirectional emission enhancement. The measured transmittance
spectra show that, in comparison to untapered reference structures, the tapered
nanoantennas exhibit distinct wide-band spectral resonances. The performed
full-vectorial numerical calculations are in good qualitative agreement with
the measured spectra, further revealing how the near-field profiles of the
tapered nanoantennas are directly reflecting their broadband characteristics
Cascaded four-wave mixing in tapered plasmonic nanoantenna
We study theoretically the cascaded four-wave mixing (FWM) in broadband
tapered plasmonic nanoantennas and demonstrate a 300-fold increase in nonlinear
frequency conversion detected in the main lobe of the nanoantenna far-field
pattern. This is achieved by tuning the elements of the nanoantenna to resonate
frequencies involved into the FWM interaction. Our findings have a potentially
broad application in ultrafast nonlinear spectroscopy, sensing, on-chip optical
frequency conversion, nonlinear optical metamaterials and photon sources
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
Energy level dynamics across the many-body localization transition
The level dynamics across the many body localization transition is examined
for XXZ-spin model with a random magnetic field. We compare different scenaria
of parameter dependent motion in the system and consider measures such as level
velocities, curvatures as well as their fidelity susceptibilities. Studying the
ergodic phase of the model we find that the level dynamics does not reveal the
commonly believed universal behavior after rescaling the curvatures by the
level velocity variance. At the same time, distributions of level curvatures
and fidelity susceptibilities coincide with properly rescaled distributions for
Gaussian Orthogonal Ensemble of random matrices. Profound differences exists
depending on way the level dynamics is imposed in the many-body localized phase
of the model in which the level dynamics can be understood with the help of
local integrals of motion.Comment: version close to that accepted in PR
Tuneable plasmonics enabled by capillary oscillations of liquid-metal nanodroplets
Plasmonics allows manipulating light at the nanoscale, but has limitations
due to the static nature of nanostructures and lack of tuneability. We propose
and theoretically analyse a room-temperature liquid-metal nanodroplet that
changes its shape, and therefore tunes the plasmon resonance frequency, due to
capillary oscillations. We show the possibility to tune the capillary
oscillation frequency of the nanodroplet and to drive the oscillations
electrically or mechanically. Employed as a tuneable nanoantenna, the
nanodroplet may find applications in sensors, imaging, microscopy, and
medicine
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