2,316 research outputs found
Amplifying free-electron evanescent fields
We show experimentally for the first time that free-electron evanescent fields can be amplified by a plasmonic nanolayer in a manner analogous to the way in which optical fields are amplified in the poor-man's superlens
Creating superfluid vortex rings in artificial magnetic fields
Artificial gauge fields are versatile tools that allow to influence the
dynamics of ultracold atoms in Bose-Einstein condensates. Here we discuss a
method of artificial gauge field generation stemming from the evanescent fields
of the curved surface of an optical nanofibre. The exponential decay of the
evanescent fields leads to large gradients in the generalized Rabi frequency
and therefore to the presence of geometric vector and scalar potentials. By
solving the Gross-Pitaevskii equation in the presence of the artificial gauge
fields originating from the fundamental HE mode of the fibre, we show
that vortex rings can be created in a controlled manner. We also calculate the
magnetic fields resulting from the higher order HE, TE, and
TM modes and compare them to the fundamental HE mode.Comment: 8 pages, 6 figure
Electromagnetic Energy Sink
The ideal black body fully absorbs all incident rays, that is, all
propagating waves created by arbitrary sources. The known idealized realization
of a black body is the perfectly matched layer (PML), widely used in numerical
electromagnetics. However, ideal black bodies and PMLs do not interact with
evanescent fields existing near any finite-size source, and the energy stored
in these fields cannot be harvested. Here we introduce the concept of the ideal
conjugate matched layer (CML), which fully absorbs energy of both propagating
and evanescent fields of sources acting as an ideal sink for electromagnetic
energy. Conjugate matched absorbers have exciting application potentials, as
resonant attractors of electromagnetic energy into the absorber volume. We
derive the conditions on the constitutive parameters of media which can serve
as CML materials, numerically study the performance of planar and cylindrical
CML and discuss possible realizations of such materials as metal-dielectric
composites.Comment: 17 pages, 15 figure
Near-field examination of perovskite-based superlenses and superlens-enhanced probe-object coupling
A planar slab of negative index material works as a superlens with
sub-diffraction-limited imaging resolution, since propagating waves are focused
and, moreover, evanescent waves are reconstructed in the image plane. Here, we
demonstrate a superlens for electric evanescent fields with low losses using
perovskites in the mid-infrared regime. The combination of near-field
microscopy with a tunable free-electron laser allows us to address precisely
the polariton modes, which are critical for super-resolution imaging. We
spectrally study the lateral and vertical distributions of evanescent waves
around the image plane of such a lens, and achieve imaging resolution of
wavelength/14 at the superlensing wavelength. Interestingly, at certain
distances between the probe and sample surface, we observe a maximum of these
evanescent fields. Comparisons with numerical simulations indicate that this
maximum originates from an enhanced coupling between probe and object, which
might be applicable for multifunctional circuits, infrared spectroscopy, and
thermal sensors.Comment: 20 pages, 6 figures, published as open access article in Nature
Communications (see http://www.nature.com/ncomms/
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