4,014 research outputs found
Bloch-mode analysis for retrieving effective parameters of metamaterials
We introduce a new approach for retrieving effective parameters of
metamaterials based on the Bloch-mode analysis of quasi-periodic composite
structures. We demonstrate that, in the case of single-mode propagation, a
complex effective refractive index can be assigned to the structure, being
restored by our method with a high accuracy. We employ both surface and volume
averaging of the electromagnetic fields of the dominating (fundamental) Bloch
modes to determine the Bloch and wave impedances, respectively. We discuss how
this method works for several characteristic examples, and demonstrate that
this approach can be useful for retrieval of both material and wave effective
parameters of a broad range of metamaterials.Comment: 12 pages, 10 figure
Slow light in photonic crystals
The problem of slowing down light by orders of magnitude has been extensively
discussed in the literature. Such a possibility can be useful in a variety of
optical and microwave applications. Many qualitatively different approaches
have been explored. Here we discuss how this goal can be achieved in linear
dispersive media, such as photonic crystals. The existence of slowly
propagating electromagnetic waves in photonic crystals is quite obvious and
well known. The main problem, though, has been how to convert the input
radiation into the slow mode without loosing a significant portion of the
incident light energy to absorption, reflection, etc. We show that the
so-called frozen mode regime offers a unique solution to the above problem.
Under the frozen mode regime, the incident light enters the photonic crystal
with little reflection and, subsequently, is completely converted into the
frozen mode with huge amplitude and almost zero group velocity. The linearity
of the above effect allows to slow light regardless of its intensity. An
additional advantage of photonic crystals over other methods of slowing down
light is that photonic crystals can preserve both time and space coherence of
the input electromagnetic wave.Comment: 96 pages, 12 figure
Metamaterials: -classical dynamic homogenization
Metamaterials are artificial composite structures designed for controlling
waves or fields, and exhibit interaction phenomena that are unexpected on the
basis of their chemical constituents. These phenomena are encoded in effective
material parameters that can be electronic, magnetic, acoustic, or elastic, and
must adequately represent the wave interaction behaviour in the composite
within desired frequency ranges. In some cases -- for example, the low
frequency regime -- there exist various efficient ways by which effective
material parameters for wave propagation in metamaterials may be found.
However, the general problem of predicting frequency-dependent dynamic
effective constants has remained unsolved. Here, we obtain novel mathematical
expressions for the effective parameters of two-dimensional metamaterial
systems valid at higher frequencies and wavelengths than previously possible.
By way of an example, random configurations of cylindrical scatterers are
considered, in various physical contexts: sound waves in a compressible fluid,
anti-plane elastic waves, and electromagnetic waves. Our results point towards
a paradigm shift in our understanding of these effective properties, and
metamaterial designs with functionalities beyond the low-frequency regime are
now open for innovation.Comment: 14 pages (including 4 figures and 1 table) in New Journal of Physics,
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