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- Front Matter: Volume 7394
- Special Invited Session: Nanoplasmonic Sensing and Imaging: Fundamentals and Applications
- Spasers, Nanolasers, and Loss Compensation
- Superresolution in Far Field and Extraordinary Transmission
- THz Plasmonics and Related Issues
- Active Nanoplasmonics and Related Subjects
- SERS and Nanoplasmonic Sensing
- Nonlinear and Strong-field Nanoplasmonics, and Related Topics
- Ultrafast Nanoplasmonics
- Engineering Nanoplasmonic Responses I
- Nanoplasmonics in Energy Conversion and Related Subjects
- Engineering Nanoplasmonic Responses II
- Control of Optical Energy Concentration
- Novel Trends in Nanoplasmonics
- Electromagnetic Eigenstates and Resonances in Nanoplasmonic Systems
- Poster Session
Front Matter: Volume 7394
Front Matter: Volume 7394
Show abstract
This PDF file contains the front matter associated with SPIE Proceedings Volume 7394, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.
Special Invited Session: Nanoplasmonic Sensing and Imaging: Fundamentals and Applications
Exploring single-molecule SERS and single-nanoparticle plasmon microscopy
Show abstract
In this work we perform correlated structural and optical studies of single nanoparticles as well as explore the generality
of SMSERS. First, wide-field plasmon resonance microscopy is used to simultaneously determine the LSPR spectra of
multiple Ag nanoprisms, whose structure is determined using TEM. Next, the structure-property relationships for well-defined
and easily-controlled nanoparticle structures (e.g. monomers, dimers, and trimers) are studied using correlated
TEM, LSPR, and SERS measurements of individual SERS nanotags. We present the SER spectrum of reporter
molecules on a single nanotag comprised of a Au trimer. It was determined that of 40 individual nanotags, just 19
exhibited SERS. The remaining nanoparticles were established by TEM to be monomers. These results demonstrate that
SERS signal is observed from individual nanotags containing a junction or hot spot. Lastly, we explore crystal violet, a
triphenyl methane dye that was used in the seminal SMSERS investigations, and re-examine single-molecule sensitivity
using the isotopologue approach.
Adiabatic focusing of surface plasmon polaritons for label free detection of few molecules by means of Raman scattering
Show abstract
Here we report the design, the fabrication and measurement of a photonic-plasmonic device that is fully compatible
with AFM microscopy and surface enhanced Raman spectroscopy. The physical mechanism exploited is the
adiabatic compression of Surface Plasmon Polaritons which propagate along a silver nanocone generating a very
high electric field at the tip end. A photonic crystal cavity is employed to efficiently couple the external laser
radiation with the nanocone. The reported measurements demonstrate the accumulation of the electric field at the tip
of the nanocone that allow the detection of a few molecules located near the tip end. The estimated Raman
enhancement factor is about 106 with respect to a standard configuration. The present results open a good
perspective for the development of an integrated Raman-AFM microscopy able to perform both topography and
chemical mapping in label free condition with a spatial resolution comparable to the tip end.
Spasers, Nanolasers, and Loss Compensation
Metallic nano-cavity lasers at near infrared wavelengths
Show abstract
There has been considerable interest in nano-cavity lasers, both from a scientific perspective for investigating
fundamental properties of lasers and cavities, and also to produce smaller and better lasers for low-power applications.
Light confinement on a wavelength scale has been reported in photonic crystal nano-cavities. Even stronger light
confinement can be achieved in metallic cavities which can confine light to volumes with dimensions considerably
smaller than the wavelength of light. It was commonly believed, however, that the high losses in metals are prohibitive
for laser operation in metallic nano-cavities. Recently we have reported lasing in a metallic nano-cavity filled with an
electrically pumped semiconductor. Importantly, the manufacturing approach employed for these devices permits even
greater miniaturization of the laser. In particular Metal-Insulator-Metal (MIM) waveguides with dimensions well below
the diffraction limit can be fabricated using our techniques. Experimental results from such MIM waveguide lasers will
be presented. In theory it is shown that it is possible to reduce the semiconductor gain medium dimensions of these MIM
waveguide devices down to a few tens of nanometers in size. Finally, latest results for the fabrication of MIM type
waveguide devices will also be examined.
Superresolution in Far Field and Extraordinary Transmission
Natural superoscillation of random functions in one and more dimensions
Show abstract
Superoscillations are regions of band-limited waves where the local wavenumber, defined as the local phase
gradient, exceeds the global maximum wavenumber in the Fourier spectrum. In random functions, defined as
superpositions of plane waves with random complex amplitudes and directions, considerable regions are naturally
superoscillatory (M. R. Dennis, et al., Opt. Lett. 33, 2976-2978, 2008; M. V. Berry and M. R. Dennis, J. Phys. A:
Math. Theor. 42, 022003, 2009). We discuss this result by deriving the joint probability density function for
intensity and phase gradient of isotropic complex random wave in any dimension, with specific reference to the
one-dimensional case.
Nanoscale slit arrays as planar far-field lenses
Show abstract
We report the first experimental demonstration of far-field lensing using a plasmonic slit array. We implement a planar
nano-slit lens using a combination of thin film deposition and focused ion beam milling. Our lens structures consist of
optically thick gold films with micron-size arrays of closely-spaced, nanoscale slits of varying widths milled using a
focused ion beam. We demonstrate experimentally that it acts as a far-field cylindrical lens for light at optical
frequencies. We show excellent agreement between the full electromagnetic field simulations of the design, which
include both evanescent and propagating modes, and the far-field, diffraction-limited confocal measurements on
manufactured structures. The flexibility offered by these slit-based planar lenses allows for the design of microlenses
that compensate for oblique illumination in integrated opto-electronic systems, such as complementary metal-oxide
semiconductor (CMOS) image sensors.
THz Plasmonics and Related Issues
Flexible and reconfigurable terahertz metamaterials
H. Tao,
A. C. Strikwerda,
K. Fan,
et al.
Show abstract
Metamaterial and plasmonic composites have led to the realization that new possibilities abound for creating materials
displaying functional electromagnetic properties not realized by nature. Recently, we have extended these ideas by
combining metamaterial elements - specifically, split ring resonators - with MEMS technology. This has enabled the
creation of non-planar flexible composites and micromechanically active structures where the orientation of the
electromagnetically resonant elements can be precisely controlled with respect to the incident field. Such adaptive
structures are the starting point for the development of a host of new functional electromagnetic devices which take
advantage of designed and tunable anisotropy.
Polarization dependent terahertz spectroscopy of a single subwavelength hole in thin metallic film
Show abstract
We theoretically and experimentally investigate the optical properties of a subwavelength hole in a thin metallic
film. The microscopic origin of the hole plasmon resonance is a collective state formed by propagating thin film
surface plasmons of wavelengths equal to integer fractions of the hole diameter. We show that the plasmon
resonance depend strongly on the polarization of the incident light. We also, using time-domain terahertz
spectroscopy, demonstrate the first experimental observation of the optical coupling between antibonding film
plasmon modes and perpendicularly polarized light to the film surface.
THz anomalous transmission in plasmonic lattices: incidence angle dependence
Show abstract
The phenomenon of anomalous transmission through subwavelength aperture arrays in metallic films (plasmonic
lattices) is thought to be mediated by surface plasmon polaritons (SPP) on the film surfaces. Using terahertz time-domain
spectroscopy we systematically studied the anomalous transmission spectrum through plasmonic lattices as a
function of the incidence angle, θ of the impinging beam. We observed splitting of the various transmission resonances
into two resonance branches when θ deviates from normal incidence that depends on the polarization direction of the
beam respect to the plane of incidence and θ. We show that the transmission resonance splitting is not related to
dispersion relation of different SPP branches, but rather is associated to the interference properties of the SPP waves on
the metal surface. The dependence of the split resonant frequencies vs. θ is fit with a theoretical formula that takes into
account the effective dielectric function of the plasmonic lattice vs. θ, which emphasizes the important role of the Fanotype
anti-resonances in the transmission spectrum. Finally, we introduced a simple way for making an efficient notch
filter with high Q factor exploiting the splitting of transmission resonance under rotation.
Active Nanoplasmonics and Related Subjects
Giant surface plasmon induced drag effect (SPIDEr) in metal nanowires
Show abstract
Here, for the first time we predict a giant surface plasmon-induced drag effect (SPIDEr), which exists under
conditions of the extreme nanoplasmonic confinement. Under realistic conditions, in nanowires, this giant SPIDEr
generates rectified THz potential differences up to 10 V and extremely strong electric fields up to ~ 105 ~ 106
V/cm. The SPIDEr is an ultrafast effect whose bandwidth for nanometric wires is ~ 20 THz. The giant SPIDEr
opens up a new field of ultraintense THz nanooptics with wide potential applications in nanotechnology and
nanoscience, including microelectronics, nanoplasmonics, and biomedicine.
SERS and Nanoplasmonic Sensing
Interface effects in hybrid gold/vanadium dioxide nanostructures
Show abstract
Gold/vanadium dioxide nanoparticles (NPs) were produced with the intention of creating a hybrid NP retaining
the characteristic semiconductor-metal phase transition of VO2 and the plasmonic properties of gold. The fabrication
procedure for arrays of the hybrid structure is presented with optical characterization and analysis of
the plasmonic structure. The high-temperature anneal required to insure the stoichiometry of the VO2 leads to
dewetting of the Au from the underlying VO2 layer, and to dramatic reshaping of the gold NP. Surface enhanced
Raman spectroscopy verifies the retention of the VO2 crystalline structure and phase transition; white light
extinction measurements exhibit the polarization sensitive plasmonic resonance peaks that characterize the electronic
signature of the phase transition. Together these techniques show that the composite system experiences
no significant intermingling between the two materials during processing. Furthermore, the controllable nature
of the extent of dewetting, via aspect ratio of the pre-annealed particle, suggests that the hybrid system will give
insight into interface interactions between the optical and structural properties of the constituents. A second
method is suggested to circumvent the annealing effect. The conclusions of our investigation suggest applications
as both a thermally or optically tunable plasmonic structure.
Fluctuation in surface enhanced Raman scattering intensity due to plasmon related heating effect
Show abstract
Temporal changes in signal intensity of Surface Enhanced Raman Scattering (SERS) upon laser excitation is an
interesting phenomenon in plasmonics. In-depth understanding of the phenomena is highly important especially when
developing a SERS sensor based on the intensity variation of particular Raman peak/band. One of the main challenges in
such a technique is the intensity reduction at a given location upon consecutive measurements. Previously, signal loss in
SERS measurement was attributed to the electric-field induced roughness relaxations in the SERS active surface. In such
cases, as the surface is smoothened out, signals are completely lost. In our observation, the reduction in the spectral
intensity is irreversible but never completely lost and a major part of it can be attributed to the plasmon induced heating
effect. Here, we experimentally demonstrate this effect by studying the SERS signal from four different Raman active
molecules adsorbed onto substrates that contain uniform nano-roughened bi-metallic silver/gold coating. Possible
mechanism that leads to irreversible signal loss is explained. Moreover, solutions for minimising such plasmonic heating
when developing a biosensor are also discussed.
Nonlinear and Strong-field Nanoplasmonics, and Related Topics
High harmonics generation by plasmonic field enhancement
Show abstract
High harmonic generation is a well-established optical method to produce coherent short-wavelength light in the
ultraviolet and soft-X ray range. This nonlinear conversion process requires ultrashort pulse lasers of strong intensity
exceeding the threshold of 1013 Wcm-2 to ionize noble gas atoms. Chirped pulse amplification (CPA) is popularly used to
increase the intensity power of a femtosecond laser produced from an oscillator. However, CPA requires long cavities
for multi-staged power amplification, restricting its practical uses due to hardware bulkiness and fragility. Recently, we
successfully exploited the phenomenon of localized surface plasmon resonance for high harmonic generation, which
enables replacing CPA with a compact metallic nanostructure. Surface plasmon resonance induced in a well-designed
nanostructure allows for intensity enhancement of the incident laser field more than 20 dB. For experimental validation,
a 2D array of gold bowtie nanostructure was fabricated on a sapphire substrate by the focused-ion-beam process. By
injection of argon and xenon gas atoms onto the bowtie nanostructure, high harmonics up to 21st order were produced
while the incident laser intensity remains at only 1011 Wcm-2. In conclusion, the approach of exploiting surface plasmons
resonance offers an important advantage of hardware compactness in high harmonic generation.
Design of nanostructures for high harmonic generation by localized surface plasmon resonance
Show abstract
When a metallic nanostructure is illuminated by ultrashort light pulses, the excitation of surface plasmons is observed
along with subsequent strong enhancement of the electric field in the vicinity of the nanostructure. This localized surface
plasmonic resonance is exploited to generate coherent extreme ultraviolet light and soft-X ray by interacting noble gas
atoms with femtosecond laser pulses. The resulting field enhancement is much affected by the 3-D shape of the used
nanostructure, so various nanostructure shapes are examined through finite-difference time-domain analysis to predict
their performance in high harmonic generation.
Ultrafast Nanoplasmonics
Saturable absorption of femtosecond laser pulses at surface plasmon resonance in gold nanoshells
Show abstract
In this work, we present an investigation of the nonlinear optical properties of nanoshells of different size in solutions
and deposited on glass substrates using a single beam z-scan method at a wavelength of 806 nm with laser duration of
170 fs. Structural properties of gold nanoshells of about 150 and 220 nm, prepared in water, are characterized by AFM
and TEM microscopy. It is found that, in general, they behave as saturable absorbers. The level of saturation depends on
the relative overlap between the plasmon resonance of nanoshells and the laser excitation wavelengths. The nonlinear
absorption coefficient, obtained by fitting the experimental results, is of the order of -10-11 cmW-1.
Engineering Nanoplasmonic Responses I
Infrared spectroscopy of antenna resonances
Show abstract
Metal nanowires with proper length give strong antenna-like plasmonic resonances in the infrared. Their resonance
spectrum is a sensitive measure not only of their geometry but also of their conductivity as we will show for lead
nanoantennae here.
Nanoplasmonics in Energy Conversion and Related Subjects
Plasmonic nanorectennas for energy conversion
Show abstract
There is renewed interest in using rectennas (consisting of an antenna coupled to a rectifying diode) for energy conversion applications. Progress in nanofabrication has enabled nanoscale devices to be fabricated, such that "nanoantennas" exist that resonate at visible/near-infrared (vis/nir) wavelengths, and ultrafast "nanodiodes" exist that can rectify vis/nir frequencies (above 1014 Hz). Photon energies are so high at these frequencies that existing theories of diode responsivity may not apply, justifying new simulations and experiments. We present modeling and experiments of nanoantenna-coupled nanodiodes, such as metal-insulator-metal structures, and discuss how our findings influence models of energy conversion in these structures. We simulate and measure the properties of potential nanorectennas such as gold nanowires on ultrathin insulators.
Engineering Nanoplasmonic Responses II
Plasmonic gold structures with individually designed geometries
Show abstract
Individual small gold structures of different sizes and shapes are fabricated on planar substrates for subsequent
characterization of their optical properties. In the process, a combination of thin-film metallization, electron beam
lithography and ion milling is employed, where electron beam structured hydrogen silsesquioxane is used as an etch
mask for the underlying gold layer. Gold cones, vertical rods, cups and flat disks can be prepared with a typical height of
about 100 nm. Their optical properties are investigated by confocal optical microscopy using a parabolic mirror for both
laser focusing and signal collection. As an example, the photoluminescence signal collected from an array of gold cones
is shown.
Control of Optical Energy Concentration
Coupling dynamics between photoluminescent centers in ZnO and surface plasmons
Show abstract
Nanostructured metal-ZnO systems provide an ideal workbench for studying the dynamics of exciton-plasmon coupling.
In order to characterize the interactions, we grew tri-layer structures comprising thin films of ZnO, variable-thickness
spacer layers of MgO, and thin films of Ag or Au. Analysis of the photoluminescence of these structures as a function
of increasing MgO thickness confirms the existence of surface plasmon polariton-exciton coupling through Purcell
enhancement of the excitonic emission for MgO films thinner than 30 nm, and through emission at the SPP resonance
for MgO films thicker than 30 nm. Further, we demonstrate the enhancement of the ZnO impurity photoluminescence
through dipole-dipole scattering with Ag and Au LSPs. Preliminary degenerate band-edge pump-probe measurements
confirm the conclusions developed from photoluminescence measurements. In order to disentangle and further quantify
the interactions seen in these systems, we are lithographically patterning metal nanoparticle arrays and metal hole arrays
on ZnO quantum wells and beginning to perform white-light pump-probe spectroscopy to fully characterize the
dynamics of energy transfer within these systems.
Novel Trends in Nanoplasmonics
Spinoptics: spin symmetry breaking in plasmonic nanostructures
Show abstract
The spin-Hall effect - the influence of the intrinsic spin on the electron trajectory, which produces transverse
deflection of the electrons, is a central tenet in the field of spintronics. Apparently, the handedness of the light's
polarization (optical spin up/down) may provide an additional degree of freedom in nanoscale photonics. The direct
observation of optical spin-Hall effect that appears when a wave carrying spin angular momentum interacts with
plasmonic nanostructures is presented. The measurements verify the unified geometric phase, demonstrated by the
observed spin-dependent deflection of the surface waves as well as spin-dependent enhanced transmission through
coaxial nanoapertures even in rotationally symmetric structures. Moreover, spin-orbit interaction is demonstrated by
use of inhomogeneous and anisotropic subwavelength dielectric structures. The observed effects inspire one to
investigate other spin-based plasmonic effects and to propose a new generation of optical elements for nanophotonic
applications.
Observation of plasmon resonance linewidth narrowing in embedded gold nanoparticle arrays
Show abstract
We demonstrate enhanced diffractive coupling resulting in sharpened extinction resonances in periodic arrays of metal
nanoparticles embedded effectively below the substrate surface. Strongly enhanced near fields with large spatial overlap
with the substrate material are shown to be associated with these extinction features. In particle arrays fabricated on
substrates there is a phase velocity mismatch between light propagating above and below the substrate surface, which
hinders diffractive coupling and access to such narrow resonances. In contrast, the embedding of the particle arrays
beneath the substrate surface, achieved via an etching procedure, offers a more homogeneous dielectric background
which improves the diffractive coupling, resulting in the sharp features associated with strong near field enhancements.
All-optical absorption switches in subwavelength metal-dielectricmetal plasmonic waveguides
Show abstract
We theoretically investigate the properties of absorption switches for metal-dielectric-metal (MDM) plasmonic
waveguides. We show that a MDM waveguide directly coupled to a cavity filled with an active material with tunable
absorption coefficient can act as an absorption switch, in which the on/off states correspond to the absence/presence of
optical pumping. We also show that a MDM plasmonic waveguide side-coupled to a cavity filled with an active material
can operate as an absorption switch, in which the on/off states correspond to the presence/absence of pumping. For a
specific modulation depth, the side-coupled-cavity switch results in more compact designs compared to the directcoupled-
cavity switch. Variations in the imaginary part of the refractive index of the material filling the cavity of
Δκ=0.01 (Δκ=0.15) result in ~60% (~99%) modulation depth. The properties of both switches can be accurately
described using transmission line theory.
Electromagnetic Eigenstates and Resonances in Nanoplasmonic Systems
Electromagnetic eigenstates applied to the theoretical discussion of meta-materials with negative refraction
Show abstract
The electromagnetic (EM) eigenstates of a thin, long circular cylinder,
for which a very good approximate closed form expression wasderived
earlier, are used to set up a numerical computation of the EM eigenstates
of a cluster of parallel cylinders. Detailed results are presented for
a pair of identical cylinders, as well as for a cluster of three
identical cylinders, where
the cylinder axes are situated at the vertices of an equilateral
triangle. The aim is to find an eigenstate that has an electric
dipole moment and a magnetic dipole moment of comparable magnitudes.
By operating the system near such an isolated resonance,
it should be possible
to tweak the macroscopic response so as to have both the macroscopic
electric permittivity εe and the macroscopic magnetic
permeability μe attain desirable values, e.g., values that are
almost real and negative.
It is argued that a three-cylinder cluster is a good configuration
for achieving this goal, but a two-cylinder cluster is not.
Plasmon resonance differences between the near- and far-field and implications for molecular detection
Show abstract
The localized surface plasmon resonance (LSPR) of a nanoplasmonic particle is often considered to occur at a single
resonant wavelength. However, the physical measures of plasmon resonance, namely the far-field measures of
scattering, absorption, and extinction, and the near-field measures of surface-average or maximum electric field
intensity, depend differently on the particle polarizability, and hence may be maximized at different wavelengths. We
show using analytic Mie theory that the differences in peak wavelength between the near- and far-fields can reach over
200 nm for nanoparticle sizes commonly used in spectroscopy applications. Using finite element analysis, we also
consider the effect of varying particle shape to spheroidal geometries, and consider polarization dependence. Using the
quasi-static and extended quasi-static approximation, we show that the differences between the near- and far- field
measures of plasmon resonance can be largely explained by radiation damping effects. We suggest that accounting for
these differences is relevant both for optimizing device design, and for improving fundamental understanding of surface-enhanced
mechanisms such as surface-enhanced Raman spectroscopy (SERS).
Designing plasmonic systems: applications to dark modes in nanoparticle pairs and triplets
Show abstract
The design of structures capable of producing strong electric near-fields has become an active area of plasmonics
research with applications including sensor technology, surface enhanced Raman scattering and plasmon solar cells. The
purposeful design of plasmonic systems is complicated by the problem of finding analytical solutions to Maxwell's
equations. Recently we developed a theory, based on a simplification of the boundary element method (BEM), for
modeling the interaction between plasmonic nanoparticles mediated by their evanescent electric fields. The theory makes
extensive use of "electrostatic" resonances in which the nanoparticle system is taken to be much smaller than the
wavelength of the exciting radiation. The key result is an expression describing the "electrostatic" coupling between
arbitrarily-shaped particle pairs, expressed in terms of their resonant eigenmodes. Simple analyses of two and three
particle systems predict the formation of "dark modes" in which the dipole scattering cross section becomes small but the
evanescent electric fields remain large.
Poster Session
Nonlinear magneto-optical transversal Kerr effect in magneto-plasmonic nanosandwiches
Show abstract
Optical properties of a planar array of composite Au/Co/Au magnetic plasmonic nanosandwiches of 60 and 110 nm in
diameter are studied using linear absorption and optical second harmonic generation (SHG) technique. Linear absorption
spectrum reveals a peak centered at about 2.1 eV, which is associated with the excitation of localized surface plasmon in
Au/Co/Au nanosandwiches. The nonlinear-optical experiments are performed using the fundamental radiation of YAG:
Nd3+ laser at 1064 nm, so that the SHG radiation corresponds to the resonant plasmon line. It is shown that in spite of
spatial inhomogeneity of such an ensemble, the SHG response in the nanosandwiches of the diameter 110 nm is
presumably polarized and specular, i.e. substantially coherent. At the same time, for nanosandwiches with the diameter
of 60 nm the SHG signal is observed in the form of the hyper-Rayleigh scattering. Plasmon-assisted effects in nonlinear-optical
response of nanosandwiches reveal themselves by different relative amplitude and phase of odd in magnetization
component of the SHG field as compared with those in plasmon-free continuous trilayer structure.
Ultrafast light transmission behavior of surface plasmon excited Maxwell Garnet type Ag nanocomposite polymer
Show abstract
In the present work, we report optical and nonlinear optical properties of Ag - Polyvinyl alcohol polymer films
prepared through a chemical method. Optical absorption measurements show the surface plasmon resonance (SPR)
around 410 nm. The SPR intensity increases with annealing temperature. Open aperture z-scan measurements done using
100 femtosecond laser pulses at 400 nm show an intensity dependent nonlinear light transmission behavior.
Spatially varying near-resonant aperture arrays for beam manipulation
Show abstract
Enhanced transmission has been associated with surface wave excitation and aperture arrangement on a metallic film.
Aperture resonances, however, have been demonstrated to exist without an order in the arrangement of apertures, with
properties dependent on geometry and optical properties of the aperture filling. These resonances are accompanied by
wavelength-dependent phase shifts in the transmitted fields offering the potential for manipulation of wavefields. Here,
we present Finite Element Method simulations investigating light passing through periodic arrays of nanometric spatially
varying near-resonant slits perforated in a metallic film. We show that a tailored phase modulation can be introduced into
an incident optical wavefield by varying aperture sizes around the resonant dimensions for a particular design
wavelength, permitting control of wavefields which can be employed for beam deflection, beam focusing or for
producing a wavelength-specific spatial field change.
Critically coupled surface phonon-polariton excitation in silicon carbide
Show abstract
We observe critical coupling to surface phonon-polaritons in silicon carbide by attenuated total reflection of
mid-infrared radiation. Reflectance measurements demonstrate critical coupling by a double-scan of wavelength
and incidence angle. Critical coupling occurs when prism coupling loss is equal to losses in silicon carbide and
the substrate, resulting in maximal electric field enhancement.
Plasmon-exciton transition in iodized Ag-Cu nanostructured films
Show abstract
Ag1-xCuxI (x= 0.10, 0.20, and 0.50) thin films with thicknesses upto15 nm produced by thermal co-evaporation onto
glass substrates were systematically iodized and carefully characterized. Optical absorption spectra of uniodized Ag-Cu
films show intense surface plasmon resonance (SPR) features with maxima at 430, 445 and 445 nm for the films of
thickness 5, 10 and 15 nm respectively and a gradual transition to zincblende AgI exciton with optical signatures at 425
nm. Delayed evolution and inhomogeneous broadening of the exciton absorption at 425 nm of the spatially confined γ-
AgI nanoparticles were clearly seen by the development of Z1,2 and Z3 exciton peaks iodization kinetics being controlled
by the as-quenched Ag-Cu clusters. Cu addition not only restricts the particle size, but also favors the island type growth
mode. PL observed at 428 nm shows a thickness and Cu-composition dependent intensity suggesting the involvement of
Frenkel defects in non-radiative recombination.
Backward wave phenomenon for light propagating through a silver nanorod array
Show abstract
In this work, we use glancing angle deposition (GLAD) to fabricate a silver nanorod array. The average tilt angle and
diameter of the silver nanorod are 65° ± 5 and 323 nm, respectively. When the array is illuminated by normal incident
light, oscillating electric field parallel to the rod and perpendicular to the rod would induce the transverse and
longitudinal plasmon resonant modes. As the longitudinal plasmon mode occurs, the absorption of the array with
thickness 323nm is enhanced and the TM mode transmittance is reduced to be 0.3 percentages. The transmitted
ellipsometric parameters are measured and the phase difference between TE mode and TM mode transmission
coefficients is detected. The absolute transmission coefficient is measured by walk-off interferometer. Compared with
the relative phase, the phase of TM mode transmission coefficient becomes a negative value. It is proposed here that a
wave propagates through the "effective thin film" and acts like a backward wave in the film.
The absorption modes of a dielectric-metal-dielectric nanorod array in the Kretschmann configuration
Show abstract
The glancing angle deposition (GLAD) technique is applied to fabricate a three-layered dielectric-metal-dielectric
anisotropic thin film. The silver nanorod array is between two SiO2 nanorod arrays (NRA). The three-layered thin film is
arranged in the Kretschmann configuration and measured the reflectance of the system. The polarization conversion
reflectance is measured from this system as the plane of incidence is not coincident with the deposition plane. From the
angular spectra of reflectance for RPP, RSS, RSP and RPS (Rij, i denotes the polarization of the incident beam and j denotes
the polarization of the reflected light) measured at angles larger than critical angle, the absorption for s-polarization and
p-polarization incident light can be calculated. The resonant peaks varied with the orientation of the deposition plane are
also measured. The configuration combines polarization conversion, transverse surface plasmon resonance and
longitudinal surface plasmon resonance of the rods. Those resonances are associated with the relationship between the
rod directions and the oscillating electric field vector. The variations of the absorption peaks affected by those resonant
modes are discussed in this work.
SPR of Ag nanoparticles in photothermochromic glasses
Show abstract
Noble metal nanoparticles (MNPs) are widely used for fabrication of metal-dielectric plasmonic nanostructures with
optical properties attractive for applications. The MNPs embedded in a glass matrix are known to exhibit an intense color
related to the resonance oscillation of the free conduction electrons known as surface plasmon resonance (SPR). Silver
nanoparticles with diameter about 2 nm are shown to be formed in the subsurface layer of photothermorefractive (PTR)
glasses after electron beam irradiation with subsequent heat treatment. The type of MNPs depends on the composition of
the PTR glass. The size distribution and MNP concentration depend on irradiation dozes and heat treatment
temperatures. The report presents the technology of silver NP fabrication, experimental optical absorption spectra, low
frequency Raman scattering, and TEM images used for determination of the MNP size distribution, and simulation of
optical extinction spectra using generalized Mie model of light scattering.
Plasmonic structures fabricated by interference lithography for sensor applications
Jacson W. Menezes,
Marcelo Nalin,
Enver F. Chillcce,
et al.
Show abstract
In this work we demonstrate the use of holographic lithography for generation of large area plasmonic periodic
structures. Submicrometric array of holes, with different periods and thickness, were recorded in gold films, in areas of
about 1 cm2, with homogeneity similar to that of samples recorded by Focused Ion Beam. In order to check the
plasmonic properties, we measured the transmission spectra of the samples. The spectra exhibit the typical surface
plasmon resonances (SPR) in the infrared whose position and width present the expected behavior with the period of the
array and film thickness. The shift of the peak position with the permittivity of the surrounding medium demonstrates the
feasebility of the sample as large area sensors.
Far-field coupling in arrays of gold and gold::vanadium dioxide nanodimers
Show abstract
Previous observations on arrays of single nanoparticles (NPs) have shown that particle separation and grating
constant determine the peak extinction wavelength of the local surface plasmon resonance (LSPR). Recently, it
has been predicted that the LSPR peak extinction wavelength in arrays of nanodimers (NDs) exhibit enhanced
sensitivity to changes in the local dielectric function compared to single NPs. In order to test this prediction,
arrays of NPs, NDs and heterodimers comprising three different NP sizes were fabricated by electron-beam
lithography with various grating constants, particle diameters, and interparticle separations. Another set of
arrays were also fabricated and coated with approximately 60-nm of vanadium dioxide, which undergoes an
insulator to metal phase transition at a critical temperature near 68.C. By tuning the temperature of the
samples through the strong-correlation region around the critical temperature, we varied the effective dielectric
constant surrounding the NP arrays over a significant range. Linear extinction measurements on the arrays were
made at temperatures above and below the critical temperature, with linear polarizers placed in the incident
beam in order to distinguish between LSPR modes. Measurements show a clear dependence of LSPR sensitivity
to interparticle separation as well as the dielectric function of the surrounding medium. Finally, finite-difference
time-domain (FDTD) simulations were carried out for comparison with the experimental results.
Synthesis of generalized surface plasmon beams
Show abstract
Surface plasmon modes can be considered as the analogous to plane waves for homogeneous media. The extension
to partially coherent surface plasmon beams is obtained by means of the incoherent superposition of the
interference between surface plasmon modes whose profile is controlled associating a probability density function
to the structural parameters implicit in their representation. We show computational simulations for cosine,
Bessel, gaussian and dark hollow surface plasmon beams.
Solvent and ligand effects on the optical properties of silver nanoparticles in silica sol-gel films
Show abstract
Silver nanoparticles in sol-gel silica films have been synthesized by heat treatment in air atmosphere. We find that the
surface plasmon resonance exhibits a principal peak at 534 nm, longer wavelength than that corresponding to the
spherical silver nanoparticles in silica (400 nm). The anisotropy in the geometry of the metallic nanoparticles explains
this noticeably red shift of the silver nanoparticles. The effect of solvents (ethanol, cyclohexane and toluene) and ligand
(pyridine) on the optical properties of these nanoparticles are measured by UV-vis spectroscopy. The position of the
surface plasmon resonance varies from 534 nm up to 573 nm depending on the refractive index or the concentration of
the solvents. On the contrary, the surface plasmon resonance is gradually shifted to the blue from 534 nm up to 462 nm
when the films were immersed in pyridine due to complexing on the surface of silver nanoparticles. These results show
highest sensitivity of the surface plasmon to variations in the local environment of the nanoparticles and they suggest that
the films can be used as colorimetric sensors.
Nanoscale bowtie aperture as high efficiency light coupler with plasmonic waveguide
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Efficiently coupling far field light into a nano structure is a challenge. This limits the utility of many of the
nanophotonics devices that have been developed recently, such as waveguides carrying surface plasmon polariton modes
with subwavelength confinement and long propagation length. End fire coupling is an option but requires careful
alignment and may not be suitable for exciting densely packed arrays of waveguides. This paper investigates the use of
a nanoscale bowtie aperture as an antenna for directly coupling far field light into a nanoscale plasmonic waveguide.
The paper shows that when the aperture is designed to be resonant the coupling coefficient can be as high as 600%
relevant to the energy incident on the open area of the aperture.
Plasmon hybridization in nanoapertures for development of an efficient nanoantenna array
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Extraordinary optical transmission through nanoholes has recently taken much interest for its promise to a wide range of
applications. Enhancement of non-linear optical phenomena and the development of sensitive biosensors are among the
leading ones. As a result of recent studies on the subject, it is now widely accepted that either the non-trivial interaction
of the localized and extended surface plasmons or only the localized surface plasmons (for direct transmissions) are
responsible from the extra-ordinary light transmission effect. On the other hand, there is little conceptual understanding
for controlling the localized surface plasmonic behavior of the individual apertures and their coupling to the extended
surface plasmons. In this letter, an intuitive and straightforward picture of the extra-ordinary light transmission
phenomena is developed using basic antenna principles for the elementary plasmonic excitations and hybridization of
these plasmonic excitations in complex nano-apertures. As an example, the model is successfully applied to explain the
experimentally observed plasmonic response of the complex rectangular coaxial apertures. Experimentally measured
red-shifting of the plasmonic resonances of the rectangular coaxial-apertures with respect to those of the simple
rectangular aperture arrays are successfully described and the asymmetric nature of the plasmonic resonances are
explained in relation to strong shape anisotropies. Further enhancement of the extra-ordinary light transmission is also
predicted by the model and experimentally demonstrated by using rectangular coaxial aperture arrays as a result of
significantly larger net dipole moment in the apertures. Model is also verified by rigorous 3D-FDTD calculations.
Nanoscale materials for sensing and detection based on surface plasmon excitation
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In this paper we present the effect of gold, silver and oxide thicknesses on the sensitivity of Surface Plasmon
Resonance (SPR). SPR sensor with enhanced sensitivities can be realized based on gold/silver films. Surface
Plasmons (SP) are electromagnetic waves that transmit along the interference between a metal and a dielectric
film, and the electromagnetic wave of the surface plasmons is coupled to oscillations of free electrons in the metal.
SPR has attracted interest in many applications such as solar cells, chemical and biological sensing. The potential
sensor application by using gold/silver nanocrystal enhanced SPR phenomenon. Sensitivity is a significant
parameter to assess the sensor's performance. Essentially, sensitivity is determined by the force of light and matter
interaction.