25,049 research outputs found
Local polariton modes and resonant tunneling of electromagnetic waves through periodic Bragg multiple quantum well structures
We study analytically defect polariton states in Bragg multiple-quantum-well
structures and defect induced changes in transmission and reflection spectra.
Defect layers can differ from the host layers in three ways: exciton-light
coupling strength, exciton resonance frequency, and inter-well spacing. We show
that a single defect leads to two local polariton modes in the photonic
bandgap. These modes cause peculiarities in reflection and transmission
spectra. Each type of defect can be reproduced experimentally, and we show that
each of these plays a distinct role in the optical properties of the system.
For some defects, we predict a narrow transmission window in the forbidden gap
at the frequency set by parameters of the defect. We obtain analytical
expressions for corresponding local frequencies as well as for reflection and
transmission coefficients. We show that the presence of the defects leads to
resonant tunneling of the electromagnetic waves via local polariton modes
accompanied by resonant enhancement of the field inside the sample, even when a
realistic absorption is taken into account. On the basis of the results
obtained, we make recommendations regarding the experimental observation of the
effects studied in readily available samples.Comment: 17 pages, 10 figures, RevTex, Submitted to PR
Large Photonic Band Gaps in Certain Periodic and Quasi-Periodic Networks in two and three dimensions
The photonic band structures in certain two- and three-dimensional periodic
networks made of one-dimensional waveguides are studied by using the
Floquet-Bloch theorem. We find that photonic band gaps exist only in those
structures where the fundamental loop exhibits anti-resonant transmission. This
is also true for quasi-periodic networks in two and three dimensions, where the
photonic band structures are calculated from the spectra of total transmission
arising from a source inside the samples. In all the cases we have studied, it
is also found that the gap positions in a network are dictated by the
frequencies at which the anti-resonance occurs.Comment: 7 pages, 10 figures and 1 table. Published in Phys. Rev. B, 70,
125104 (2004
Negative Refractive Index in Optics of Metal-Dielectric Composites
Specially designed metal-dielectric composites can have a negative refractive
index in the optical range. Specifically, it is shown that arrays of single and
paired nanorods can provide such negative refraction. For pairs of metal rods,
a negative refractive index has been observed at 1.5 micrometer. The inverted
structure of paired voids in metal films may also exhibit a negative refractive
index. A similar effect can be accomplished with metal strips in which the
refractive index can reach -2. The refractive index retrieval procedure and the
critical role of light phases in determining the refractive index is discussed.Comment: 39 pages, 17 figures, 24 equation
Polarization switching and nonreciprocity in symmetric and asymmetric magnetophotonic multilayers with nonlinear defect
A one-dimensional magnetophotonic crystal with a nonlinear defect placed
either symmetrically or asymmetrically inside the structure is considered.
Simultaneous effects of time-reversal nonreciprocity and nonlinear spatial
asymmetry in the structure are studied. Bistable response is demonstrated in a
such system, accompanied by abrupt polarization switching between two circular
or elliptical polarizations for transmitted and reflected waves. The effect is
explained in terms of field localization at defect-mode spectral resonances and
can be used in the design of thin-film optical isolators and polarization
transformation devices.Comment: 20 pages, 8 figure
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