1,721,006 research outputs found
Photonic crystals for optimal color conversion in light-emitting diodes: a semi-analytical approach
Get PDFBased on effective-medium approximation, we analytically optimize the color conversion of GaN-based lightemitting p-n junctions, with respect to the size and spatial density of the used photonic crystals (PhCs), being filled with quantum dots (QDs). The model is two-dimensional and the incoherent excitation into the multiple quantum wells is mimicked by line sources of random electric and magnetic currents. Optimal operation is achieved by suppressing the radiation extraction for one visible color and simultaneously maximizing the emission for another color. For these cases, the field gets inevitably concentrated into the PhCs of QDs, where the conversion occurs, and the performance of the device is maximized. Several examples from these ultra-performing designs are provided, within which a secondary sweep can be applied by posing extra constraints related to cost or ease of fabrication.</p
Optimally Sharp Energy Filtering of Quantum Particles via Homogeneous Planar Inclusions
Get PDFSome of the most influential players from academia and industry have recently expressed concrete interest for quantum engineering applications, especially for new concepts in controlling and processing the quantum signals traveling into condensed matter. An important operation when manipulating particle beams behaving as matter waves concerns filtering with respect to their own energy; such an objective can be well-served by a single planar inclusion of specific size and texture embedded into suitable background. A large number of inclusion/host combinations from realistic materials are tried and the optimally sharp resonance regimes, which correspond to performance limits for such a simplistic structure, are carefully identified. These results may inspire efforts towards the generalization of the adopted approach and the translation of sophisticated inverse design techniques, already successfully implemented for nanophotonic setups, into quantum arena
“Unlocking” the Ground: Increasing the Detectability of Buried Objects by Depositing Passive Superstrates
Get PDFOne of the main problems when trying to detect
the position and other characteristics of a small inclusion into
lossy earth via external measurements is the inclusion’s poor
scattering response due to attenuation. Hence, increasing the
scattered power generated by the inclusion by using not an active
but a passive material is of great interest. To this direction, we
examine, in this work, a procedure of “unlocking” the ground by
depositing a thin passive layer of conventional material atop of
it. The first step is to significantly enhance the transmission into
a lossy half space, in the absence of the inclusion, by covering
it with a passive slab. The redistribution of the fields into the
slab and the infinite half space, due to the interplay of waves
between the interfaces, makes possible to determine the thickness
and permittivity of an optimal layer. The full boundary value
problem (including the inclusion and the deposited superstrate) is
solved semi-analytically via integral equations techniques. Then,
the scattered power of the buried inclusion is compared to the
corresponding quantity when no additional layer is present.
We report substantial improvement in the detectability of the
inclusion for several types of ground and burying depths by using
conventional realizable passive materials. Implementation aspects
in potential applications as well as possible future generalizations
are also discussed. The developed technique may constitute an
effective “configuration (structural) preprocessing” which may
be used as a first step in the analysis of related problems before
the application of an inverse scattering algorithm concerning the
efficient processing of the scattering dat
NANOTUBES AS SINKS FOR QUANTUM PARTICLES
Get PDFNanotubes with proper thickness, size
and texture make ultra-efficient sinks for
the quantum particles traveling into spe cific background media. Several optimal
semiconducting cylindrical layers are re ported to achieve enhancement in the trap ping of matter waves by 2-3 orders of mag nitude. The identified shells can be used
as pieces in quantum devices that involve
the focusing of incident beams from charge
pumps and superconducting capacitors to
radiation pattern controllers and matter wave lense
DESIGNING NANOINCLUSIONS FOR QUANTUM SENSING BASED ON ELECTROMAGNETIC SCATTERING FORMALISM
Get PDFQuantum interactions between a single particle and nanoinclusions of spherical or cylindrical
shape are optimized to produce scattering lineshapes of high selectivity with respect to impinging
energies, excitation directions, and cavity sizes. The optimization uses a rigorous solution derived via
electromagnetic scattering formalism while the adopted scheme rejects boundary extrema corresponding
to resonances that occur outside of the permissible parametric domains. The reported effects may inspire
experimental efforts towards designing quantum sensing systems employed in applications spanning from
quantum switching and filtering to single-photon detection and quantum memory
Optical PT-Symmetric Counterparts of Ordinary Metals
Get PDFHow one can fabricate the Parity-Time (PT) symmetric
siblings of commonly used metals in the visible? This
work tries to give an answer to that question by providing
the features of the active media which conjugately pair the
complex permittivities of ordinary metals (Copper, Aluminum,
Silver, Gold, Platinum) at the optical frequencies. The frequency
response model of quantum dots (QDs) is used to evaluate the
effective permittivity of the active material; their characteristics
which give a PT-symmetric counterpart for the considered
metal are deduced through a multi-step optimization process.
The required resonance frequencies, loss factors and degrees
of population inversion for the QDs are provided for various
frequencies and metals. The response of the metals when they
are PT-symmetrically coupled with the provided mixtures is
demonstrated in specific photonic configurations and interesting
properties with certain applicability potential are reveale
ANALYTICAL INVERSE DESIGN OF POLARIZATION-INSENSITIVE PHOTONIC FILTERS BY TAILORING FABRY-PEROT INTERFERENCE
Get PDFFiltering of photonic signals of a certain frequency while suppressing all the others of a specific band for both electromagnetic signal polarizations, becomes possible with a single dielectric layer by properly engineering the occurred Fabry-Perot interference. Analytical formulas for combinations of cavity size, material texture and incoming angle are given so that the filtering purpose is optimally served. In this way, inverse design for a simple class of optical setups is rigorously performed and, if the employed medium is very dense and the working band narrow enough, sharp filters with increased frequency selectivity are obtained
ANOMALOUS DIFFRACTION OF MATTER WAVES WITH MINIMAL QUANTUM METASURFACES
Get PDFIn the last few years, there is a huge upsurge in the number of closed deals regarding quantum technologies for materials, computing, communication and instrumentation. Such a trend has inevitably affected the research funding market; thus, large state initiatives are taken that are directly expected to drive the formulation of novel research concepts and the development of quantum device prototypes from sensors and circuitry to quantum memory and repeaters. A fundamental operation behind all these applications is the effective steering of electrons, constituting matter waves, along specific directions and with certain magnitudes, due to development of various reflective and refractive orders. The objective of this study is to optimize the simplest structure that supports such anomalous diffraction, namely a quantum metasurface comprising cylindrical rods embedded in suitable crystalline matter. Several highly-performing designs from these minimal setups are proven to work exceptionally as multiport components, employable to a variety of quantum engineering implementations
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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