1,120 research outputs found
Weak Measurements of Light Chirality with a Plasmonic Slit
We examine, both experimentally and theoretically, an interaction of tightly
focused polarized light with a slit on a metal surface supporting
plasmon-polariton modes. Remarkably, this simple system can be highly sensitive
to the polarization of the incident light and offers a perfect
quantum-weak-measurement tool with a built-in post-selection in the
plasmon-polariton mode. We observe the plasmonic spin Hall effect in both
coordinate and momentum spaces which is interpreted as weak measurements of the
helicity of light with real and imaginary weak values determined by the input
polarization. Our experiment combines advantages of (i) quantum weak
measurements, (ii) near-field plasmonic systems, and (iii) high-numerical
aperture microscopy in employing spin-orbit interaction of light and probing
light chirality.Comment: 5 pages, 3 figure
Conductivity in organic semiconductors hybridized with the vacuum field
Organic semiconductors have generated considerable interest for their
potential for creating inexpensive and flexible devices easily processed on a
large scale [1-11]. However technological applications are currently limited by
the low mobility of the charge carriers associated with the disorder in these
materials [5-8]. Much effort over the past decades has therefore been focused
on optimizing the organisation of the material or the devices to improve
carrier mobility. Here we take a radically different path to solving this
problem, namely by injecting carriers into states that are hybridized to the
vacuum electromagnetic field. These are coherent states that can extend over as
many as 10^5 molecules and should thereby favour conductivity in such
materials. To test this idea, organic semiconductors were strongly coupled to
the vacuum electromagnetic field on plasmonic structures to form polaritonic
states with large Rabi splittings ca. 0.7 eV. Conductivity experiments show
that indeed the current does increase by an order of magnitude at resonance in
the coupled state, reflecting mostly a change in field-effect mobility as
revealed when the structure is gated in a transistor configuration. A
theoretical quantum model is presented that confirms the delocalization of the
wave-functions of the hybridized states and the consequences on the
conductivity. While this is a proof-of-principle study, in practice
conductivity mediated by light-matter hybridized states is easy to implement
and we therefore expect that it will be used to improve organic devices. More
broadly our findings illustrate the potential of engineering the vacuum
electromagnetic environment to modify and to improve properties of materials.Comment: 16 pages, 13 figure
Temperature dependence of electric resistance and magnetoresistance of pressed nanocomposites of multilayer nanotubes with the structure of nested cones
Bulk samples of carbon multilayer nanotubes with the structure of nested
cones (fishbone structure) suitable for transport measurements, were prepared
by compressing under high pressure (~25 kbar) a nanotube precursor synthesized
through thermal decomposition of polyethylene catalyzed by nickel. The
structure of the initial nanotube material was studied using high-resolution
transmission electron microscopy. In the low-temperature range (4.2 - 100 K)
the electric resistance of the samples changes according to the law ln \rho ~
(T_0/T)^{1/3}, where T_0 ~ 7 K. The measured magnetoresistance is quadratic in
the magnetic field and linear in the reciprocal temperature. The measurements
have been interpreted in terms of two-dimensional variable-range hopping
conductivity. It is suggested that the space between the inside and outside
walls of nanotubes acts as a two-dimensional conducting medium. Estimates
suggest a high value of the density of electron states at the Fermi level of
about 5 10^{21} eV^{-1} cm^{-3}.Comment: 8 pages, 4 figures. EM photographic images on figures 1a, 1b, 1c
attached as JPG files. For correspondence mail to [email protected]
Observation of Enhanced Beaming from Photonic Crystal Waveguides
We report on the experimental observation of the beaming effect in photonic
crystals enhanced via surface modes. We experimentally map the spatial field
distribution of energy emitted from a subwavelength photonic crystal waveguide
into free-space, rendering with crisp clarity the diffractionless beaming of
energy. Our experimental data agree well with our numerical studies of the
beaming enhancement in photonic crystals with modulated surfaces. Without loss
of generality, we study the beaming effect in a photonic crystal scaled to
microwave frequencies and demonstrate the technological capacity to deliver
long-range, wavelength-scaled beaming of energy.Comment: 4 pages, 6 figure
Active control of focal length and beam deflection in a metallic nano-slit array lens with multiple sources
We propose a surface plasmon-polariton based nano-rod array lens structure
that incorporates two additional lateral input channels, with the ability to
control the focal length and the deflection of the transmitted beam through the
lens actively by the intensity of the channel sources. We demonstrate by
numerical simulations that, applying the sources with the same intensity can
change the focal point and the beam waist, whereas unequal intensities generate
an asymmetric field profile in the nano-rod array inducing an off-axis beam
deflection.Comment: 4 pages, 5 figure
Optical control of photon tunneling through an array of nanometer scale cylindrical channels
We report first observation of photon tunneling gated by light at a different
wavelength in an artificially created array of nanometer scale cylindrical
channels in a thick gold film. Polarization properties of gated light provide
strong proof of the enhanced nonlinear optical mixing in nanometric channels
involved in the process. This suggests the possibility of building a new class
of "gated" photon tunneling devices for massive parallel all-optical signal and
image processing.Comment: 4 pages, 4 figure
Conditional Reverse Tet-Transactivator Mouse Strains for the Efficient Induction of TRE-Regulated Transgenes in Mice
Tetracycline or doxycycline (dox)-regulated control of genetic elements allows inducible, reversible and tissue specific regulation of gene expression in mice. This approach provides a means to investigate protein function in specific cell lineages and at defined periods of development and disease. Efficient and stable regulation of cDNAs or non-coding elements (e.g. shRNAs) downstream of the tetracycline-regulated element (TRE) requires the robust expression of a tet-transactivator protein, commonly the reverse tet-transactivator, rtTA. Most rtTA strains rely on tissue specific promoters that often do not provide sufficient rtTA levels for optimal inducible expression. Here we describe the generation of two mouse strains that enable Cre-dependent, robust expression of rtTA3, providing tissue-restricted and consistent induction of TRE-controlled transgenes. We show that these transgenic strains can be effectively combined with established mouse models of disease, including both Cre/LoxP-based approaches and non Cre-dependent disease models. The integration of these new tools with established mouse models promises the development of more flexible genetic systems to uncover the mechanisms of development and disease pathogenesis
Theory of extraordinary optical transmission through subwavelength hole arrays
We present a fully three-dimensional theoretical study of the extraordinary
transmission of light through subwavelength hole arrays in optically thick
metal films. Good agreement is obtained with experimental data. An analytical
minimal model is also developed, which conclusively shows that the enhancement
of transmission is due to tunneling through surface plasmons formed on each
metal-dielectric interfaces. Different regimes of tunneling (resonant through a
''surface plasmon molecule", or sequential through two isolated surface
plasmons) are found depending on the geometrical parameters defining the
system.Comment: 4 pages, 4 figure
Disclination vortices in elastic media
The vortex-like solutions are studied in the framework of the gauge model of
disclinations in elastic continuum. A complete set of model equations with
disclination driven dislocations taken into account is considered. Within the
linear approximation an exact solution for a low-angle wedge disclination is
found to be independent from the coupling constants of the theory. As a result,
no additional dimensional characteristics (like the core radius of the defect)
are involved. The situation changes drastically for 2\pi vortices where two
characteristic lengths, l_\phi and l_W, become of importance. The asymptotical
behaviour of the solutions for both singular and nonsingular 2\pi vortices is
studied. Forces between pairs of vortices are calculated.Comment: 13 pages, published versio
Geometrically induced modification of surface plasmons in the optical and telecom regimes
We demonstrate that the introduction of a subwavelength periodic modulation
into a metallic structure strongly modifies the guiding characteristics of the
surface plasmon modes supported by the system. Moreover, it is also shown how a
new type of a tightly confined surface plasmon polariton mode can be created by
just milling a periodic corrugation into a metallic ridge placed on top of a
metal surface
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