347 research outputs found
Non-reciprocal optical reflection from a bidimensional array of subwavelength holes in a metallic film
Using simulations and theoretical arguments we investigate the specular
reflection of a perforated gold film deposited on a glass substrate. A square
lattice of cylindrical holes is assumed to produce the periodic lateral
corrugation needed to hybridize the surface plasmons with radiative states. It
is shown that, contrasting transmission approaches, a knowledge of the
reflection on either side of the film provides separate information on the
gold-vacuum surface plasmons and on the gold-glass interface plasmons. Recent
experimental data on a specific implementation of this system are reexamined;
these show a good agreement between the measured reflections and the
simulations in both directions of incident wave probes. This confirms the
importance of taking into account the reflection asymmetry in the far-field
assessment of surface plasmons properties.Comment: 4 pages, 3 figures. Published versio
Bounded modes to the rescue of optical transmission
This paper presents a brief survey of the evolution of knowledge about
diffraction gratings. After recalling some basic facts, historically and
physically, we introduce the concept of Wood anomalies. Next, we present some
recent works in order to introduce the role of bounded modes in transmission
gratings. The consequences of these recent results are then introduced. This
paper is a secondary publication, published in Europhysics News (EPN 38, 3
(2007) 27-31). In the present version, some additional notes have been added
with related references.Comment: 6 pages, 6 figures. Secondary publication. Brief revie
Role of Wood anomalies in optical properties of thin metallic films with a bidimensional array of subwavelength holes
Recents works deal with the optical transmission on arrays of subwavelength
holes in a metallic layer deposited on a dielectric substrate. Making the
system as realistic as possible, we perform simulations to enlighten the
experimental data. This paper proposes an investigation of the optical
properties related to the transmission of such devices. Numerical simulations
give theoretical results in good agreement with experiment and we observe that
the transmission and reflection behaviour correspond to Fano's profile
correlated with resonant response of the eigen modes coupled with
nonhomogeneous diffraction orders. We thus conclude that the transmission
properties observed could conceivably be explained as resulting from resonant
Wood's anomalies.Comment: 7 pages, 10 figures, 2 table
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Improved light extraction in the bioluminescent lantern of a Photuris firefly (Lampyridae)
A common problem of light sources emitting from an homogeneous
high-refractive index medium into air is the loss of photons by total internal
reflection. Bioluminescent organisms, as well as artificial devices, have to
face this problem. It is expected that life, with its mechanisms for evolution,
would have selected appropriate optical structures to get around this problem,
at least partially. The morphology of the lantern of a specific firefly in the
genus Photuris has been examined. The optical properties of the different parts
of this lantern have been modeled, in order to determine their positive or
adverse effect with regard to the global light extraction. We conclude that the
most efficient pieces of the lantern structure are the misfit of the external
scales (which produce abrupt roughness in air) and the lowering of the
refractive index at the level of the cluster of photocytes, where the
bioluminescent production takes place.Comment: 13 pages, 11 figures, published in Optics Expres
Nanomorphology of the blue iridescent wings of a giant tropical wasp, "Megascolia procer javanensis" (Hymenoptera)
The wings of the giant wasp "Megascolia Procer Javanensis" are opaque and
iridescent. The origin of the blue-green iridescence is studied in detail,
using reflection spectroscopy, scanning electron microscopy and physical
modelling. It is shown that the structure responsible for the iridescence is a
single homogeneous transparent chitin layer covering the whole surface of each
wing. The opacity is essentially due to the presence of melanin in the
stratified medium which forms the mechanical core of the wing.Comment: 8 pages, 7 figures. Improved version. Accepted for publication in
Phys. Rev.
Light transmission assisted by Brewster-Zennek modes in chromium films carrying a subwavelength hole array
This work confirms that not only surface plasmons but many other kinds of
electromagnetic eigenmodes should be considered in explaining the values of the
transmittivity through a slab bearing a two-dimensional periodic corrugation.
Specifically, the role of Brewster-Zennek modes appearing in metallic films
exhibiting regions of weak positive dielectric constant. It is proposed that
these modes play a significant role in the light transmission in a thin
chromium film perforated with normal cylindrical holes, for appropriate lattice
parameters.Comment: 5 pages, 4 figures. Published versio
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