5,285 research outputs found
Abnormal enhancement of electric field inside a thin permittivity-near-zero object in free space
It is found that the electric field can be enhanced strongly inside a
permittivity-near-zero object in free space, when the transverse cross section
of the object is small and the length along the propagation direction of the
incident wave is large enough as compared with the wavelength. The physical
mechanism is explained in details. The incident electromagnetic energy can only
flow almost normally through the outer surface into or out of the
permittivity-near-zero object, which leads to large energy stream density and
then strong electric field inside the object. Meanwhile, the magnetic field
inside the permittivity-near-zero object may be smaller than that of the
incident wave, which is also helpful for enhancing the electric field. Two
permittivity-near-zero objects of simple shapes, namely, a thin cylindrical
shell and a long thin rectangular bar, are chosen for numerical illustration.
The enhancement of the electric field becomes stronger when the
permittivity-near-zero object becomes thinner. The physical mechanism of the
field enhancement is completely different from the plasmonic resonance
enhancement at a metal surface
Into New Lands: the Principle of Navigation
The principle address at the Forty-fourth commencement of the Rice Institute on May 31, 195
Squeezing electromagnetic energy with a dielectric split ring inside a permeability-near-zero metamaterial
A novel electromagnetic energy squeezing mechanism is proposed based on the
special properties of permeability-near-zero metamaterials. Nearly no energy
stream can enter a conventional dielectric region positioned inside a
permeability-near-zero material. When a source is surrounded by a dielectric
split ring (encloser with a gap opened), the electromagnetic energy generated
by the source is forced to propagate through the gap. When the gap is narrow,
the energy stream density becomes very large and makes the magnetic field
enhanced drastically in the gap. The narrow gap can be long and bended. This
provides us a method to obtain strong magnetic field without using resonance
enhancement.Comment: 17pages, 4 figure
Non-Linear Deformations of Liquid-Liquid Interfaces Induced by Electromagnetic Radiation Pressure
The idea of working with a near-critical phase-separated liquid mixture
whereby the surface tension becomes weak, has recently made the field of laser
manipulation of liquid interfaces a much more convenient tool in practice. The
deformation of interfaces may become as large as several tenths of micrometers,
even with the use of conventional laser power. This circumstance necessitates
the use of nonlinear geometrical theory for the description of surface
deformations. The present paper works out such a theory, for the surface
deformation under conditions of axial symmetry and stationarity. Good agreement
is found with the experimental results of Casner and Delville [A. Casner and J.
P. Delville, Phys. Rev. Lett. {\bf 87}, 054503 (2001); Opt. Lett. {\bf 26},
1418 (2001); Phys. Rev. Lett. {\bf 90}, 144503 (2003)], in the case of moderate
power or a broad laser beam. In the case of large power and a narrow beam,
corresponding to surface deformations of about 50 micrometers or higher, the
theory is found to over-predict the deformation. Possible explanations of this
discrepancy are discussed.Comment: RevTeX4, 19 pages, 4 figures. Sec. IIIB rewritten, 4 new references.
To appear in Phys. Rev.
Associations between selected demographic, biological, school environmental and physical education based correlates, and adolescent physical activity
The study investigated associations between selected physical activity correlates among 299 adolescents (90 boys, age 12-14 years) from 3 English schools. Physical activity was assessed by self-report and accelerometry. Correlates represented biological, predisposing, and demographic factors as described in the Youth Physical Activity Promotion Model. Boys engaged in more self-reported (p < .01) and accelerometer assessed physical activity than girls (p = .02). Positive associations between sex (male), BMI, Perceived PE Ability, Perceived PE Worth, number of enrolled students, and physical activity outcomes were evident (p < .05). Schoolbased physical activity promotion should emphasize sex-specific enhancement of students' perceived PE competence and enjoyment
Bessel beam propagation: Energy localization and velocity
The propagation of a Bessel beam (or Bessel-X wave) is analyzed on the basis
of a vectorial treatment. The electric and magnetic fields are obtained by
considering a realistic situation able to generate that kind of scalar field.
Specifically, we analyze the field due to a ring-shaped aperture over a
metallic screen on which a linearly polarized plane wave impinges. On this
basis, and in the far field approximation, we can obtain information about the
propagation of energy flux and the velocity of the energy.Comment: 6 pages, 4 figure
Non-Paraxial Accelerating Beams
We present the spatially accelerating solutions of the Maxwell equations.
Such non-paraxial beams accelerate in a circular trajectory, thus generalizing
the concept of Airy beams. For both TE and TM polarizations, the beams exhibit
shape-preserving bending with sub-wavelength features, and the Poynting vector
of the main lobe displays a turn of more than 90 degrees. We show that these
accelerating beams are self-healing, analyze their properties, and compare to
the paraxial Airy beams. Finally, we present the new family of periodic
accelerating beams which can be constructed from our solutions
Efficient channeling of fluorescence photons from single quantum dots into guided modes of optical nanofiber
We experimentally demonstrate the efficient channeling of fluorescence
photons from single q-dots on optical nanofiber into the guided modes, by
measuring the photon-count rates through the guided and radiation modes
simultaneously. We obtain the maximum channeling efficiency to be 22.0
(\pm4.8)% at fiber diameter of 350 nm for the emission wavelength of 780 nm.
The results may open new possibilities in quantum information technologies for
generating single photons into single-mode optical-fibers.Comment: 5 pages, 4 figure
Delay-bandwidth and delay-loss limitations for cloaking of large objects
Based on a simple model of ground-plane cloaking, we argue that the diffculty
of cloaking is fundamentally limited by delay-loss and delaylbandwidth/size
limitations that worsen as the size of the object to be cloaked increases
relative to the wavelength. These considerations must be taken into account
when scaling experimental cloaking demonstrations from wavelength-scale objects
towards larger sizes, and suggest quantitative material/loss challenges in
cloaking human-scale objects.Comment: 4 pages, 2 figure
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