810 research outputs found
Radiative Heat Transfer between Neighboring Particles
The near-field interaction between two neighboring particles is known to
produce enhanced radiative heat transfer. We advance in the understanding of
this phenomenon by including the full electromagnetic particle response, heat
exchange with the environment, and important radiative corrections both in the
distance dependence of the fields and in the particle absorption coefficients.
We find that crossed terms of electric and magnetic interactions dominate the
transfer rate between gold and SiC particles, whereas radiative corrections
reduce it by several orders of magnitude even at small separations. Radiation
away from the dimer can be strongly suppressed or enhanced at low and high
temperatures, respectively. These effects must be taken into account for an
accurate description of radiative heat transfer in nanostructured environments.Comment: 22 pages, 9 figures, fully self-contained derivation
Electromagnetic surface states in structured perfect-conductor surfaces
Surface-bound modes in metamaterials forged by drilling periodic hole arrays
in perfect-conductor surfaces are investigated by means of both analytical
techniques and rigorous numerical solution of Maxwell's equations. It is shown
that these metamaterials cannot be described in general by local,
frequency-dependent permittivities and permeabilities for small periods
compared to the wavelength, except in certain limiting cases that are discussed
in detail. New related metamaterials are shown to exhibit exciting optical
properties that are elucidated in the light of our simple analytical approach.Comment: 5 figure
Vacuum friction in rotating particles
We study the frictional torque acting on particles rotating in empty space.
At zero temperature, vacuum friction transforms mechanical energy into light
emission and produces particle heating. However, particle cooling relative to
the environment occurs at finite temperatures and low rotation velocities.
Radiation emission is boosted and its spectrum significantly departed from a
hot-body emission profile as the velocity increases. Stopping times ranging
from hours to billions of years are predicted for materials, particle sizes,
and temperatures accessible to experiment. Implications for the behavior of
cosmic dust are discussed.Comment: 4 figures, 10 pages, includes paper and supplementary information in
the appendi
Full transmission through perfect-conductor subwavelength hole arrays
Light transmission through 2D subwavelength hole arrays in perfect-conductor
films is shown to be complete (100%) at some resonant wavelengths even for
arbitrarily narrow holes. Conversely, the reflection on a 2D planar array of
non-absorbing scatterers is shown to be complete at some wavelengths regardless
how weak the scatterers are. These results are proven analytically and
corroborated by rigorous numerical solution of Maxwell's equations. This work
supports the central role played by dynamical diffraction during light
transmission through subwavelength hole arrays and it provides a systematics to
analyze more complex geometries and many of the features observed in connection
with transmission through hole arrays.Comment: 5 pages, 4 figure
Diacritical study of light, electrons, and sound scattering by particles and holes
We discuss the differences and similarities in the interaction of scalar and
vector wave-fields with particles and holes. Analytical results are provided
for the transmission of isolated and arrayed small holes as well as surface
modes in hole arrays for light, electrons, and sound. In contrast to the
optical case, small-hole arrays in perforated perfect screens cannot produce
acoustic or electronic surface-bound states. However, unlike electrons and
light, sound is transmitted through individual holes approximately in
proportion to their area, regardless their size. We discuss these issues with a
systematic analysis that allows exploring both common properties and unique
behavior in wave phenomena for different material realizations.Comment: 3 figure
Optical coherence transfer mediated by free electrons
We theoretically investigate the quantum-coherence properties of the cathodoluminescence (CL) emission produced by a temporally modulated electron beam. Specifically, we consider the quantum-optical correlations of CL produced by electrons that are previously shaped by a laser field. Our main prediction is the presence of phase correlations between the emitted CL field and the electron-modulating laser, even though the emission intensity and spectral profile are independent of the electron state. In addition, the coherence of the CL field extends to harmonics of the laser frequency. Since electron beams can be focused to below 1 Ă…, their ability to transfer optical coherence could enable the ultra-precise excitation, manipulation, and spectrally resolved probing of nanoscale quantum systems
Microphotonic parabolic light directors fabricated by two-photon lithography
We have fabricated microphotonic parabolic light directors using two-photon lithography, thin-film processing, and aperture formation by focused ion beam lithography. Optical transmission measurements through upright parabolic directors 22 μm high and 10 μm in diameter exhibit strong beam directivity with a beam divergence of 5.6°, in reasonable agreement with ray-tracing and full-field electromagnetic simulations. The results indicate the suitability of microphotonic parabolic light directors for producing collimated beams for applications in advanced solar cell and light-emitting diode designs
The role of electromagnetic trapped modes in extraordinary transmission in nanostructured materials
We assert that the physics underlying the extraordinary light transmission
(reflection) in nanostructured materials can be understood from rather general
principles based on the formal scattering theory developed in quantum
mechanics. The Maxwell equations in passive (dispersive and absorptive) linear
media are written in the form of the Schr\"{o}dinger equation to which the
quantum mechanical resonant scattering theory (the Lippmann-Schwinger
formalism) is applied. It is demonstrated that the existence of long-lived
quasistationary eigenstates of the effective Hamiltonian for the Maxwell theory
naturally explains the extraordinary transmission properties observed in
various nanostructured materials. Such states correspond to quasistationary
electromagnetic modes trapped in the scattering structure. Our general approach
is also illustrated with an example of the zero-order transmission of the
TE-polarized light through a metal-dielectric grating structure. Here a direct
on-the-grid solution of the time-dependent Maxwell equations demonstrates the
significance of resonances (or trapped modes) for extraordinary light
transmissioComment: 14 pages, 6 figures; Discussion in Section 4 expanded; typos
corrected; a reference added; Figure 4 revise
- …