76 research outputs found
The multipole description of complex plasmonic nanostructures
Zusammenfassend konnte gezeigt werden, dass mit der Multipolentwicklung bis zur zweiten Ordnung sowohl die mikroskopischen als auch die makroskopischen optischen Eigenschaften von Metamaterialien in konsistenter Form beschrieben werden können. Zu Grunde liegt der dabei eingesetzten und sehr allgemeinen Methode ein spezielles mikroskopisches Modell zur Beschreibung der Ladungsträgerdynamik in der Struktur. In dieser Arbeit wurde dafür ein System gekoppelter Oszillatoren eingesetzt, welches allerdings auch durch andere Modelle oder Methoden ersetzt werden kann. Diese einfachen Annahmen reichten jedoch aus, um eine qualitative und quantitative Beschreibung der komplizierten Licht-Materie Wechselwirkung in den untersuchten Metamaterialien zu erhalten. Diese Art der Modellierung bestehend aus mikroskopischer Ladungsträgerbeschreibung und anschließender Multipolentwicklung ist ein wesentliches Resultat dieser Arbeit. Für die Erforschung der Metamaterialien stellt diese Methode ein physikalisches, analytisches und methodisch intuitives Werkzeug dar, um auch komplexere Strukturen verstehen oder gezielt entwerfen zu können
Using effective medium theories to design tailored nanocomposite materials for optical systems
Modern optical systems are subject to very restrictive performance, size and
cost requirements. Especially in portable systems size often is the most
important factor, which necessitates elaborate designs to achieve the desired
specifications. However, current designs already operate very close to the
physical limits and further progress is difficult to achieve by changing only
the complexity of the design. Another way of improving the performance is to
tailor the optical properties of materials specifically to the application at
hand. A class of novel, customizable materials that enables the tailoring of
the optical properties, and promises to overcome many of the intrinsic
disadvantages of polymers, are nanocomposites. However, despite considerable
past research efforts, these types of materials are largely underutilized in
optical systems. To shed light into this issue we, in this paper, discuss how
nanocomposites can be modeled using effective medium theories. In the second
part, we then investigate the fundamental requirements that have to be
fulfilled to make nanocomposites suitable for optical applications, and show
that it is indeed possible to fabricate such a material using existing methods.
Furthermore, we show how nanocomposites can be used to tailor the refractive
index and dispersion properties towards specific applications.Comment: This is a draft manuscript of a paper published in Proc. SPIE
(Proceedings Volume 10745, Current Developments in Lens Design and Optical
Engineering XIX, Event: SPIE Optical Engineering + Applications, 2018
Transparency in Formal Proof
The oft-emphasized virtue of formal proof is correctness; a machine-checked proof adds greatly to our confidence in a result. But the rigors of formalization give rise to another possible virtue, namely clarity. Given the state of the art, clarity and formality are at odds: complexity of formalization obscures the content of proof. To address this, we develop a notion of proof strategies which extend the well-known notion of proof tactics. Beginning with the foundations of logic, we describe the methods and structures necessary to implement proof strategies, concluding with a proof-of-concept implementation in CheQED, a web-based proof assistant
Decomposing the scattered field of two-dimensional metaatoms into multipole contributions
We introduce a technique to decompose the scattered near field of
two-dimensional arbitrary metaatoms into its multipole contributions. To this
end we expand the scattered field upon plane wave illumination into cylindrical
harmonics as known from Mie theory. By relating these cylin- drical harmonics
to the field radiated by Cartesian multipoles, the contribution of the lowest
order electric and magnetic multipoles can be identified. Revealing these
multipoles is essential for the design of metamaterials because they largely
determine the character of light propagation. In par- ticular, having this
information at hand it is straightforward to distinguish between effects that
result either from the arrangement of the metaatoms or from their particular
design
Verfassungsrechtliche Grundlagen der Raumplanung
Den verfassungsrechtlichen Hintergrund der Raumplanung bilden die Gesetzgebungs- und Planungskompetenzen, die kommunale Selbstverwaltungsgarantie, das Grundrecht auf Eigentum sowie weitere verfassungsrechtliche Prinzipien. Die Raumplanung beruht auf einer Vielzahl von Kompetenztiteln. Einfluss auf die Raumplanung und ihre Teilaspekte nehmen dabei Grundrechte, Staatszielbestimmungen und grundrechtsgleiche Rechte
Plasmonic rod dimers as elementary planar chiral meta-atoms
Electromagnetic response of metallic rod dimers is theoretically calculated
for arbitrary planar arrangement of rods in the dimer. It is shown that dimers
without an in-plane symmetry axis exhibit elliptical dichroism and act as
"atoms" in planar chiral metamaterials. Due to a very simple geometry of the
rod dimer, such planar metamaterials are much easier in fabrication than
conventional split-ring or gammadion-type structures, and lend themselves to a
simple analytical treatment based on coupled dipole model. Dependencies of
metamaterial's directional asymmetry on the dimer's geometry are established
analytically and confirmed in numerical simulations.Comment: 3 page
Electromagnetic multipole theory for optical nanomaterials
Optical properties of natural or designed materials are determined by the
electromagnetic multipole moments that light can excite in the constituent
particles. In this work we present an approach to calculate the multipole
excitations in arbitrary arrays of nanoscatterers in a dielectric host medium.
We introduce a simple and illustrative multipole decomposition of the electric
currents excited in the scatterers and link this decomposition to the classical
multipole expansion of the scattered field. In particular, we find that
completely different multipoles can produce identical scattered fields. The
presented multipole theory can be used as a basis for the design and
characterization of optical nanomaterials
- …