1,533 research outputs found
Omnidirectionally Bending to the Normal in epsilon-near-Zero Metamaterials
Contrary to conventional wisdom that light bends away from the normal at the
interface when it passes from high to low refractive index media, here we
demonstrate an exotic phenomenon that the direction of electromagnetic power
bends towards the normal when light is incident from arbitrary high refractive
index medium to \epsilon-near-zero metamaterial. Moreover, the direction of the
transmitted beam is close to the normal for all angles of incidence. In other
words, the electromagnetic power coming from different directions in air or
arbitrary high refractive index medium can be redirected to the direction
almost parallel to the normal upon entering the \epsilon-near-zero
metamaterial. This phenomenon is counterintuitive to the behavior described by
conventional Snell's law and resulted from the interplay between
\epsilon-near-zero and material loss. This property has potential applications
in communications to increase acceptance angle and energy delivery without
using optical lenses and mechanical gimbals
Resonant Transmission of Electromagnetic Fields through Subwavelength Zero- Slits
We theoretically investigate the transmission of electromagnetic radiation
through a metal plate with a zero- metamaterial slit, where the
permittivity tends towards zero over a given bandwidth. Our analytic results
demonstrate that the transmission coefficient can be substantial for a broad
range of slit geometries, including subwavelength widths that are many
wavelengths long. This novel resonant effect has features quite unlike the
Fabry-P\'{e}rot-like resonances that have been observed in conductors with deep
channels. We further reveal that these high impedance ultranarrow
zero- channels can have significantly {\it greater} transmission
compared to slits with no wave impedance difference across them
Infra-Red Surface-Plasmon-Resonance technique for biological studies
We report on a Surface-Plasmon-Resonance (SPR) technique based on Fourier
-Transform - Infra - Red (FTIR) spectrometer. In contrast to the conventional
surface plasmon technique, operating at a fixed wavelength and a variable angle
of incidence, our setup allows the wavelength and the angle of incidence to be
varied simultaneously. We explored the potential of the SPR technique in the
infrared for biological studies involving aqueous solutions. Using computer
simulations, we found the optimal combination of parameters (incident angle,
wavelength) for performing this task. Our experiments with physiologically
important glucose concentrations in water and in human plasma verified our
computer simulations. Importantly, we demonstrated that the sensitivity of the
SPR technique in the infrared range is not lower and in fact is even higher
than that for visible light. We emphasize the advantages of infra red SPR for
studying glucose and other biological molecules in living cells.Comment: 8 pages,8 figure
Ultrasmall volume Plasmons - yet with complete retardation effects
Nano particle-plasmons are attributed to quasi-static oscillation with no
wave propagation due to their subwavelength size. However, when located within
a band-gap medium (even in air if the particle is small enough), the particle
interfaces are acting as wave-mirrors, incurring small negative retardation.
The latter when compensated by a respective (short) propagation within the
particle substantiates a full-fledged resonator based on constructive
interference. This unusual wave interference in the deep subwavelength regime
(modal-volume<0.001lambda^3) significantly enhances the Q-factor, e.g. 50
compared to the quasi-static limit of 5.5.Comment: 16 pages, 6 figure
Mode-balancing far field control of light localization in nanoantennas
Light localization is controlled at a scale of lambda/10 in the harmonic
regime from the far field domain in a plasmonic nanoantenna. The nanoantenna
under study consists of 3 aligned spheres 50 nm in diameter separated by a
distance of 5 nm. By simply tuning the orientation of an incident plane wave,
symmetric and antisymmetric mode-balancing induces a strong enhancement of the
near field intensity in one cavity while nullifying the light intensity in the
other cavity. Furthermore, it is demonstrated that the dipolar moment of a
plasmonic particle can be fully extinguished when strongly coupled with a dimer
of identical nanoparticles. Consequently, optical transparency can be achieved
in an ultra-compact symmetric metallic structure
Giant circular dichroism of a molecule in a region of strong plasmon resonances between two neighboring gold nanocrystals
We report on giant circular dichroism (CD) of a molecule inserted into a
plasmonic hot spot. Naturally occurring molecules and biomolecules have
typically CD signals in the UV range, whereas plasmonic nanocrystals exhibit
strong plasmon resonances in the visible spectral interval. Therefore,
excitations of chiral molecules and plasmon resonances are typically
off-resonant. Nevertheless, we demonstrate theoretically that it is possible to
create strongly-enhanced molecular CD utilizing the plasmons. This task is
doubly challenging since it requires both creation and enhancement of the
molecular CD in the visible region. We demonstrate this effect within the model
which incorporates a chiral molecule and a plasmonic dimer. The associated
mechanism of plasmonic CD comes from the Coulomb interaction which is greatly
amplified in a plasmonic hot spot.Comment: Manuscript: 4+pages, 4 figures; Supplemental_Material: 10 pages, 7
figure
Curvature-induced radiation of surface plasmon polaritons propagating around bends
We present a theoretical study of the curvature-induced radiation of surface
plasmon polaritons (SPPs) propagating around bends at metal-dielectric
interfaces. We explain qualitatively how the curvature leads to distortion of
the phase front, causing the fields to radiate energy away from the
metal-dielectric interface. We then quantify, both analytically and
numerically, radiation losses and energy transmission efficiencies of SPPs
propagating around bends with varying radii- as well as sign-of-curvature.Comment: 9 pages, 8 figures, submitted to Physical Review
Dynamical excitonic effects in metals and semiconductors
The dynamics of an electron--hole pair induced by the time--dependent
screened Coulomb interaction is discussed. In contrast to the case where the
static electron--hole interaction is considered we demonstrate the occurrence
of important dynamical excitonic effects in the solution of the Bethe--Salpeter
equation.This is illustrated in the calculated absorption spectra of noble
metals (copper and silver) and silicon. Dynamical corrections strongly affect
the spectra, partially canceling dynamical self--energy effects and leading to
good agreement with experiment.Comment: Accepted for publication on Phys. Rev. Let
Surface plasmon resonance assisted rapid laser joining of glass
Rapid and strong joining of clear glass to glass containing randomly distributed embedded spherical silver nanoparticles upon nanosecond pulsed laser irradiation (∼40 ns and repetition rate of 100 kHz) at 532 nm is demonstrated. The embedded silver nanoparticles were ∼30–40 nm in diameter, contained in a thin surface layer of ∼10 μm. A joint strength of 12.5 MPa was achieved for a laser fluence of only ∼0.13 J/cm2 and scanning speed of 10 mm/s. The bonding mechanism is discussed in terms of absorption of the laser energy by nanoparticles and the transfer of the accumulated localised heat to the surrounding glass leading to the local melting and formation of a strong bond. The presented technique is scalable and overcomes a number of serious challenges for a widespread adoption of laser-assisted rapid joining of glass substrates, enabling applications in the manufacture of microelectronic devices, sensors, micro-fluidic, and medical devices
Semiconductor-metal nanoparticle molecules: hybrid excitons and non-linear Fano effect
Modern nanotechnology opens the possibility of combining nanocrystals of
various materials with very different characteristics in one superstructure.
The resultant superstructure may provide new physical properties not
encountered in homogeneous systems. Here we study theoretically the optical
properties of hybrid molecules composed of semiconductor and metal
nanoparticles. Excitons and plasmons in such a hybrid molecule become strongly
coupled and demonstrate novel properties. At low incident light intensity, the
exciton peak in the absorption spectrum is broadened and shifted due to
incoherent and coherent interactions between metal and semiconductor
nanoparticles. At high light intensity, the absorption spectrum demonstrates a
surprising, strongly asymmetric shape. This shape originates from the coherent
inter-nanoparticle Coulomb interaction and can be viewed as a non-linear Fano
effect which is quite different from the usual linear Fano resonance.Comment: 5 pages, 5 figures, submitted to Phys. Rev. Let
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