714 research outputs found
Resonantly suppressed transmission and anomalously enhanced light absorption in ultrathin metal films
We study light diffraction in the periodically modulated ultrathin metal
films both analytically and numerically. Without modulation these films are
almost transparent. The periodicity results in the anomalous effects, such as
suppression of the transmittance accompanied by a strong enhancement of the
absorptivity and specular reflectivity, due to excitation of the surface
plasmon polaritons. These phenomena are opposite to the widely known enhanced
transparency of periodically modulated optically thick metal films. Our
theoretical analysis can be a starting point for the experimental investigation
of these intriguing phenomena.Comment: 4 pages, 5 figure
Investigation of the spectra of coupled polaritons on the periodically modulated metallic layer and the narrow regions of anomalous transparency
The paper deals with the theoretical investigation of plane, normally
incident electromagnetic wave transmission through the flat metal film whose
dielectric constant has small periodical sinusoidal modulation in one dimension
parallel to the projection of the electric field onto the film surface. The
dependencies of the film transmittancy on the parameters of the problem
(frequency, modulation depth and absorption) are examined. It is shown that the
film transmittancy increases considerably when the conditions for resonance
interaction of an incident electromagnetic wave with surface plasmon polaritons
(SPPs) are met. It is found that for small but finite absorption there are two
frequencies in the vicinity of which the transmittancy can achieve the values
of the order of unity due to resonances on symmetric and antisymmetric
(relative to the mean plane) SPP modes. It is shown that for each value of
absorption there exists a certain optimal modulation depth, which maximizes the
resonance transparency.Comment: 18 pages, 8 figures, proceeding of conference "Plasmonics: metallic
nanostructures and their optical properties", SPIE's 48-th Annual Meeting,
3-8 August, 2003, San Diego, US
New mechanism for non-trivial intra-molecular vibrational dynamics
We investigate the time evolution process of one selected (initially prepared
by optical pumping) vibrational molecular state, coupled to all other
intra-molecular vibrational states of the same molecule, and also to its
environment. Molecular states forming the first reservoir are characterised by
a discrete dense spectrum, whereas the environment reservoir states form a
continuous spectrum. Assuming the equidistant reservoir states we find the
exact analytical solution of the quantum dynamic equations. System reservoirs
couplings yield to spontaneous decay of the states, whereas system-reservoir
exchange leads to recurrence cycles and Loschmidt echo and double resonances at
the interlevel reservoir transitions. Due to these couplings the system
time evolution is not reduced to a simple exponential relaxation. We predict
various regimes of the system dynamics, ranging from exponential decay to
irregular damped oscillations. Namely, we show that there are four possible
dynamic regimes of the evolution: (i) - independent of the environment
exponential decay suppressing backward transitions, (ii) Loschmidt echo regime,
(iii) - incoherent dynamics with multicomponent Loschmidt echo, when the system
state exchanges its energy with many states of the reservoir, (iv) - cycle
mixing regime, when the long term system dynamics appear to be random. We
suggest applications of our results for interpretation of femtosecond vibration
spectra of large molecules and nano-systems.Comment: 11 pages, 2 figure
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