An eigenvalue analysis of plasmonic waveguides built in a general layered medium is introduced by combining the Multiple Multipole Program (MMP) with modified layered media Green's functions (LMGF). The new method, first, provides the possible locations of the eigenvalues on a given complex plane (called search functions in the MMP analysis), which provides a very useful information when locating the eigenvalues not only by MMP but also by other numerical methods. Special eigenvalue search and tracing routines are then used to determine the exact locations of the eigenvalues around the possible locations provided by the search functions. The details of the MMP and the modification on LMGF is introduced, together with various numerical examples demonstrating the efficiency of the method.
An upgrade for the efficiency proven electromagnetic simulation tool, Multiple Multipole Program (MMP) is
proposed, in order to efficiently analyze plasmonic structures in layered geometries. In this upgrade, a new
expansion set, the layered media Green's function, is included in the open source EM simulation package Open-
MaX, which contains the latest version of MMP. By this upgrade the advantages of both the MMP and layered
media Green's functions are combined and an efficient and robust simulation tool for the analysis of structures
in layered geometries in optical range of the spectrum is obtained. In this paper, the fundamentals of MMP and
the derivation of layered media Green's functions will be discussed. Numerical results will also be included in
order to demonstrate the efficiency of the upgraded method.
Layered media Green's functions are introduced as an additional expansion set for the Multiple Multipole Program
(MMP). By using these new expansions, the necessity of matching the boundary conditions along the
infinite boundaries in the layered geometry is eliminated. As the result, OpenMaX, the open-source platform
that includes the latest version of MMP, becomes more user friendly and robust when handling photonic structures
in layered media. A description of both MMP and the layered media Green's functions, together with
various numerical examples are introduced to demonstrate the efficiency of the method.
In this work we study optical response of noble metal nanoparticles and report how it may be controllably varied over a
wide range of wavelengths. Altering the particle shape and materials we investigate the surface plasmon resonances of
nanostars. To design novel nanostructures possessing diverse optical properties we assemble several plasmonic materials
into a single nanoparticle. With numerical simulation tool based on the spectral boundary integral equation method we
investigate far-field and near-field characteristics of a variety of metal, metal-dielectric and bimetal nanostructures to be
used in a range of applications from disease diagnostics through to the identification of contraband.
While tapered and coated fibers are used as probes for scanning near-field optical microscopy SNOM), tapered
coaxial probes and other structures are used in the microwave regime for broad band measurements. Aperture
probes, tapered fibers and tapered waveguides have the inherent disadvantage that the radiation will have to
pass a cutoff region. This is not the case for coaxial probes and for appropriately chosen transmission lines based
on metallic wires. To enhance the energy transition for a tapered SNOM tip, the cladding can be split by milling
longitudinal slits in it. We demonstrate the principle of mode conversion in the microwave region, building a tip
for a scanning near-field microwave microscope SNMM) with a feed similar to a SNOM tip with the slits in the
cladding. Transition to a single wire mode is made at the very end of the tip. With this new kind of SNMM tip
we scan a test structure and demonstrate a resolution of 1/882 wavelengths for double passage operation.
Using advanced mathematical techniques for optical computing and combining them with advanced optical engineering
techniques and understanding of physical and chemical processes in plasmonic materials we developed novel boundary
integral equation based numerical simulation tool. The performances of numerical simulation tool were investigated by
means of extensive numerical studies of plasmonic nanostuctures including nanostructures with periodically and
aperiodically spaced nanoparticles embedded in homogenenous medium, isolated homogeneous, layered and
multilayered plasmonic nanoparticles. Selecting the most pormissing particle configurations, we applied the most
efficient hierarchical method to reduce the complexity of calculation schemes for each particular nanostructure
In this work a fully three-dimensional parameterization model for the investigations of gold nanostars by the
ultraspherical Spectral Boundary Integral Equation method has been developed. The set of the numerical results provide
guidelines for a choice of the system parameters for tuning. These can be exploited for new approaches to medical
diagnoses or testing for environmental contaminants.
Shape-dependent sensitivity of localized surface plasmon-based biosensing was investigated by combining single-particle protein-sensing and multiple multipole program simulation. Significantly higher sensitivity was observed for tetrahedral particles than spherical ones, which was revealed by careful structural analysis of individually measured particles. The simulation of the corresponding particles with layered protein adsorption model showed consistent optical property and sensitivity, which were explained in terms of the field enhancement at the pointing edges.
Shape dependent sensitivity of localized surface plasmon based biosensing was investigated by combining single particle
protein sensing and multiple multipole program simulation. Significantly higher sensitivity was observed for tetrahedral
particles than spherical ones, which was revealed by careful structural analysis of individually measured particles. The
simulation of the corresponding particles with layered protein adsorption model showed consistent optical property and
sensitivity, which were explained in terms of the field enhancement at the pointing edges.
Plasmonic nano antennas are highly attractive at optical frequencies due to their strong resonances - even when their size
is smaller than the wavelength - and because of their potential of extreme field enhancement. Such antennas may be
applied for sensing of biological nano particles as well as for single molecule detection. Because of considerable material
losses and strong dispersion of metals at optical frequencies, the numerical analysis of plasmonic antennas is very
demanding. An additional difficulty is caused when very narrow gaps between nano particles are utilized for increasing
the field enhancement. In this paper we discuss the main difficulties of time domain solvers, namely FDTD and FVTD
and we compare various frequency domain solvers, namely the commercial FEM packages JCMsuite, Comsol, HFSS,
and Microwave Studio with the semi-analytic MMP code that may be used as a reference due to its fast convergence and
high accuracy. The current version of this paper has had a correction made to it at the request of the author. Please see the linked Errata for further details.
The work was devoted to the design of advanced plasmonic nanoantennas based on numerical investigation of Surface
Plasmon Polariton resonances in noble metal nanoparticles. Their dependence on the nanoparticle shape and size is
investigated for an efficient manipulation by SPP strength and excitation wavelength. Local near-field plasmon effects
and the impact of SPPs on the directivity of emission in far-field are analyzed simultaneously by means of a boundary
integral equation approach. Various particles including the shapes with gaps and sharp tips were investigated in order to
select the geometries which permit achieving of strong near-field enhancement. The investigation of crescent moon
structures demonstrated the possibility of additional field enhancement because both a gap and sharp tips are realized at
the same time. Analysis of all considered noble-metal nanoparticles revealed a mechanism of efficient manipulation by
SPPs leading to the design of several highly optimized optical nanoantennas.
The optical response of nanostructures that exhibit pronounced plasmonic effects is studied and analyzed. Various
approaches to solve light scattering problems in the time domain and in the frequency domain, using both the domain
and the boundary discretization methods were used. Far-field and near-field characteristics of plasmonic nanostructures
are investigated with several numerical algorithms to study the shape effect and the effects of the illumination angles on
the resonance behavior. Numerical results with high accuracy, reduced complexity and reduced computational time due
to extensive use of semi-analytical solutions are obtained. This set of numerical experiments demonstrates significant
differences in the performances of different numerical methods. We observed that even simple geometries of plasmonic
nanostructures may pose severe problems for various methods. We identify a strong need to select and modify numerical
simulation algorithms according to the plasmonic effects, in addition to the standard selection of numerical method
according to the geometrical settings and length scales.
The main goal of this paper is to present thorough investigations for the metallic nanoshelled structures with rigorous
electromagnetic analysis. Two metallic nanoshelled structures are investigated; namely, single nano-shelled cylinder, and
nano-shelled photonic crystals. A rigorous Maxwell's equations solver is used to get insights into the optical properties of
the structures. Our numerical simulations show that it is difficult to shift the plasmon resonance to long wavelength (e.g.
towards ten micrometers) in such a structure. Flat bands are found in the metallic nanoshelled photonic crystals when the
lattice constants are much smaller than the operating wavelength. This would become interesting especially for realizing
ultra-compact slow wave structures such as plasmonic devices with low group velocity. Several applications using
nano-shelled particles as sensors, as substrates for surface enhanced Raman spectroscopy are also discussed in the paper.
This paper presents a theoretical, numerical and experimental study for the design of a three-dimensional directive
antenna for microwave telecommunications (KU-band: 12-18 GHz) applications. The presented structure consists of a
stack of 6 metallic crossed grids above a ground plane, which is potentially capable to replace parabolic antennas,
because it is much more compact than classical solutions and uses a single patch as feeding device. Such structure acts as
a metallic photonic crystal at the band edge or as an ultra-refractive metamaterial. A numerical 3D code computing the
diffraction by metallic bi-periodic gratings, and a fast layer-by-layer approach, allows to model and to optimize this kind
of antennas. Especially, it is reported how both directivity and frequency bandwidth can be improved simultaneously.
Numerical results are confirmed by experiments in an anechoic chamber.
A Model-Based Parameter Estimation (MBPE) technique is described to accelerate numerical simulations of
electromagnetic structures. The adaptive MBPE algorithm is based on Cauchy's formula and operates in the frequency
domain to extrapolate or interpolate from a narrowband set of data to a broadband set of data. The data can be either
computed or measured over a specified frequency range. For computed data the sampled values of the function and a few
low order derivatives are calculated from a Maxwell solver and are then used to reconstruct the function. For measured
data, only measured values of the parameter set are used to create broadband information. In this case derivatives are
avoided as they are too noisy. Adaptive MBPE belongs to the class of auxiliary techniques and can be added to any field
solver. In this paper the technique is combined with two semi-analytic field solvers working in the frequency domain, the
Method of Auxiliary Sources (MAS) and the Multiple Multipole Program (MMP). A dielectric waveguide, metallic and
metallo-dielectric Photonic Crystals (PhCs) as well as Channel Plasmon-Polariton (CPP) structures are analyzed to
demonstrate the efficiency of adaptive MBPE.
Optical antennas consisting of metallic parts are analyzed using the Multiple Multipole Program (MMP), a semi-analytic
boundary discretization method. It is demonstrated that difficult numerical problems are caused because optical antennas
exhibit strong material dispersion, loss, and plasmon-polariton effects that require a very fine discretization. In addition
to standard dipole-type antennas, consisting of two pieces of metal, a new structure consisting of a single metal piece
with a tiny groove in the center is analyzed. This structure takes advantage of the Channel Plasmon-Polariton (CPP)
effect and exhibits a strong enhancement of the electric field in the groove. Furthermore, the groove type antenna
exhibits two resonance peaks when its dimension is much smaller than the wavelength. It is demonstrated that the
strengths and locations of the resonance peaks may be tuned within some range by tuning the length of the antenna.
The focus of this paper is on the numerical analysis of ultra-small metallic waveguides at optical wavelengths that is very
demanding 1) because the cross sections may be much smaller than the wavelength, 2) because strong plasmon-polariton
effects must be accounted for, and 3) because of strong dispersion and material loss. After a short outline of available
numerical methods with focus on eigenvalue solvers, the Multiple Multipole Program (MMP) - that is applied for
obtaining the results shown in this paper - is outlined. Since the analysis of metallic waveguides leads to difficult
complex eigenvalue problems, several techniques for solving such problems are introduced. Based on these procedures,
simple plasmonic wires, metallic wires coupled with a dielectric fiber, partially coated optical fibers, and metallic
waveguides with tiny V-grooves of only a few nanometers are analyzed. The impact of the material properties is
demonstrated by comparing gold and silver wires with V-grooves. It is shown that such structures may exhibit Channel
Plasmon-Polariton (CPP) modes with acceptable propagation lengths even when the grooves are only a few nm deep, but
only within a narrow frequency range and only for metals with low loss in the desired frequency range. These modes
show a strong field confinement within the groove that might be attractive for sensor applications. Furthermore, the
partially coated optical fiber is attractive for optical nearfield microscopy and exhibits field enhancement due to wedge
plasmon polariton and triple-point plasmon polariton effects.
Monolithic photonic integration offers unsurpassed perspectives for higher functional density, new functions, high per-formance, and reduced cost for the telecommunication. Advanced local material growth techniques and the emerging photonic crystal (PhC) technology are enabling concepts towards high-density photonic integration, unprecedented per-formance, multi-functionality, and ultimately optical systems-on-a-chip. In this paper, we present our achievements in photonic integration applied to the fabrication of InP-based mode-locked laser diodes capable of generating optical pulses with sub-ps duration using the heterogeneous growth of a new uni-traveling carrier ultrafast absorber. The results are compared to simulations performed using a distributed model including intra-cavity reflections at the sections inter-faces and hybrid mode-locking. We also discuss our work on InP-based photonic crystals (PhCs) for dense photonic integration. A combination of two-dimensional modeling for functional optimization and three-dimensional simulation for real-world verification is used. The fabricated structures feature more than 3.5μm deep holes as well as excellent pattern-transfer accuracy using electron-beam lithography and advanced proximity-effects correction. Passive devices such as waveguides, 60° bends and power splitters are characterized by means of the end-fire technique. The devices are also investigated using scanning-near field optical microscopy. The PhC activity is extended to the investigation of TM bandgaps for all-optical switches relying on intersubband transitions at 1.55μm in AlAsSb/InGaAs quantum wells.
The concepts of near-field optical microscopy and experimental and theoretical work carried out in Switzerland over the last 10 years are reviewed. After a description of the pioneering experiments of the mid-1980s, we focus on the recent efforts of the three Swiss laboratories currently working in the field in close collaboration. This newly refreshed initiative in near-field optics is supported by the Swiss Priority Program Optique.