Search

International audience; Semitransparent organic photovoltaics (ST-OPVs) offer promising prospects for self-powered greenhouses and building-integrated photovoltaic systems. However, a remaining critical challenge is to balance the two competing indexes of power conversion efficiency (PCE) and average visible transmittance (AVT). Herein, a synergetic strategy of light manipulation is developed to achieve high-performance ST-OPVs by employing dual photonic structures with a rear single-layer optical coupling layer (OCL) and a front single-layer antireflection coating (ARC). The material selection and thickness optimization of both OCL and ARC are systematically guided by combining theoretical simulations and experimental devices, leading to significantly enhanced light utilization in ST-OPVs. As a result, the use of dual photonic structures enables ST-OPVs based on the active layer of PM6:Y6 to demonstrate simultaneously a high AVT of 35.7% and a good PCE of 10.29%, yielding an excellent light utilization efficiency of 3.67% with a remarkable improvement of 43% comparing with that of the control device. This work provides a simple yet effective strategy of light manipulation for the development of high-performance ST-OPVs.

International audience; We explore numerically and experimentally the formation of hybridized modes between a bright mode displayed by a gold nanodisc and either dark or bright modes of a nanorod – both elements being either separated by a nanometer-size gap (disconnected system) or relied on a metal junction (connected system). In terms of modeling, we compare the scattering or absorption spectra and field distributions obtained under oblique-incidence plane wave illumination with quasi-normal mode computation and an analytical model based on a coupled oscillator model. Both connected and disconnected systems have very different plasmon properties in longitudinal polarization. The disconnected system can be consistently understood in terms of the nature of hybridized modes and coupling strength using either QNMs or coupled oscillator model; however the connected configuration presents intriguing peculiarities based on the strong redistribution of charges implied by the presence of the metal connection. In practice, the fabrication of disconnected or connected configurations depends on the mitigation of lithographic proximity effects inherent to top-down lithography methods, which can lead to the formation of small metal junctions, while careful lithographic dosing allows one to fabricate disconnected systems with a gap as low as 20 nm. We obtained a very good agreement between experimentally measured scattering spectra and numerical predictions. The methods and analyses presented in this work can be applied to a wide range of systems, for potential applications in light–matter interactions, biosensing or strain monitoring.

SSRN preprint article https://ssrn.com/abstract=4108410; International audience; Nonfullerene organic solar cells (OSCs) have recently made remarkable progress as one of the most promising next-generation photovoltaic technologies. Still, it is highly desirable to enhance the light harvesting for the sake of photoactive layer with a limited thickness. In this work, we developed efficient nonfullerene OSCs through incorporating hybrid plasmonic metal nanostructures (MNS) consisted of gold nanobipyramids (AuNBPs) and gold nanospheres (AuNSs). The synergistic localized surface plasmon resonance (LSPR) of hybrid MNS has been predesigned to perfectly match with the absorption range of nonfullerene photoactive layer especially in the near-infrared (NIR) region, subsequently delivering enhanced light harvesting and photo-response. The plasmonic enhancement mechanisms were systematically investigated by theoretical simulations and various experimental measurements, showing that hybrid MNS exhibited significant broadband near field enhancement and scattering effect as well as the advantage in electrical aspect to facilitate the charge extraction and transport. As a result, the power conversion efficiency (PCE) was improved from 15.46% to 16.62% for OSCs based on PM6:Y6 due to the synergistic plasmonic effect of hybrid MNS. Overall, this work paves the way for using plasmonic MNS with tunable optical properties as an alternative approach for the development of high-performance OSCs.

International audience; The coupling of gold nanoantennas (AuNAs) in the arrangement of monomers in bidimensional gratings is investigated both experimentally and numerically. The influence of edge diffraction, corresponding to the grazing propagation of specific diffracted orders, and the dependence of grating parameters on lattice plasmon modes are studied. It is shown that the grating pitch influences the spectral position of the Rayleigh wavelength related to the grazing diffraction in air and/or in glass. In order to investigate the effect of diffraction and its interplay with the Rayleigh wavelength, extinction measurements with different incidence angles are carried out. For incidence angles above θ=20∘, along with the excitation of quadrupolar and vertical modes, very narrow dips or sharp excitations are observed in the spectra. These ones strongly depend on the respective spectral position of Rayleigh anomaly and specific dipolar mode, on the propagation direction of the grazing diffraction, and on the considered plasmon mode. These features are explained in the light of numerical calculations obtained with Green’s tensor method. All the above different characteristics and couplings are of great practical interest, especially for a possible implementation in biosensor devices and for other technological applications spanning from precision medicine and life science to telecommunications and energy systems.

Ponencia presentada en Fifteenth International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials), 20-24 Sept. 2021, New York, USA In this work, we discuss the interaction between Helmholtz resonators, using the finite element method. We show that the coupling between two spheres gives rise to two resonant modes at low frequencies. One is symmetric and corresponds to a mono-polar breathing mode, as currently observed. The second one is anti-symmetric and behaves as a dipole. We show that the first one generates an isotropic wave in the far pressure field while the second one gives rise to a directional propagative wave. The two modes are discussed as a function of the geometrical and physical parameters. When considering the thermo-viscous properties of air for a specific set of parameters, one finds that the behavior of the dipolar mode can be changed from a diffuser to an absorber. By managing double Helmholtz resonators, we aim to create a multifunctional meta-surface operating at two different frequencies.

International audience; Understanding the interactions between nanoparticles (NPs) and boundaries of cells is crucial both for their toxicity and therapeutic applications. Besides specific receptor-mediated endocytosis of surface-functionalized NPs, passive internalization is prompted by relatively unspecific parameters, such as particle size and charge. Based on theoretical treatments, adhesion to and bending of the cell membrane can induce NP wrapping. Experimentally, powerful tools are needed to selectively probe possible membrane-NP motifs at very dilute conditions and avoid dye labeling. In this work, we employ surface resonance-enhanced dynamic light scattering, surface plasmon resonance, electron microscopy, and simulations for sensing interactions between plasmonic AuNPs and polymersomes. We distinguish three different interaction scenarios at nanomolar concentrations by tuning the surface charge of AuNPs and rationalize these events by balancing vesicle bending and electrostatic/van der Waals AuNP and vesicle adhesion. The clarification of the physical conditions under which nanoparticles passively translocate across membranes can aid in the rational design of drugs that cannot exploit specific modes of cellular uptake and also elucidates physical properties that render nanoparticles in the environment particularly toxic.

International audience; The interaction between phonons and localized plasmons in coupled nanoparticles can be exploited both for modulating the scattered electromagnetic field and the understanding of the mechanical vibrations at nanoscale. In this paper, we demonstrate by numerical analysis an enhanced optomechanical interaction in a film-coupled gold dimer nanoparticles mediated by surface acoustic waves. Two gold nanoridges are placed atop a multilayer structure consisting of a thin dielectric spacer covering a gold film layer on a silicon dioxide substrate. Numerical simulations of the optical properties reveal the existence of three surface localized plasmons in the infrared range with enhanced scattering and narrower linewidths than with a single nanoridge. The physical origin of such modes as well as their tunability as function of key geometrical parameters are successfully captured with a simple model based on effective Metal-Insulator-Metal (MIM)-like plasmonic cavity. We calculate the optomechanic coupling rates between the GHz localized mechanical modes and plasmonic modes of the dimer, finding that the strongest coupling is observed for the in-phase compressional mode followed by the out-of-phase flexural mode. Both such modes can be excited by launching a surface acoustic wave (Sezawa wave) at the inlet in front of the dimer structure. It is also found that the flexural mode which is inactive optomechanically in case of a monomer becomes active due to dimer coupling, with a significant phonon-plasmon coupling rate. The findings in this work may facilitate design of new optomechanical components monitored with fast coherent acoustics, leading to new generation of light acousto-optic modulators where strong optomechanical interactions are required.

Networks can be constructed out of finite open loops. Open loops are guides such that their one-dimensional properties may be considered independent of the open loop shape and radius. Their response function is derived from that of infinite open loops. A general definition of eigenstates is also given. The difference between resonant and force responses is made precise. These open loops have free boundary conditions at their two ends when they are used in network construction. The case of open loops with fixed end conditions is considered also. The photonic analysis is done with the Maxwell electromagnetic propagation wave equation.

In this chapter, we review numerical simulations of light propagation in one-dimensional photonic semiconductor optical waveguides coupled to one or several lateral stubs. In the presence of one stub, we show that the transmission spectrum contains several narrow dips, provided that the boundaries of the stub are covered with a perfect metal to avoid the radiation of the propagating light. Such a simulation of the metallic coating can be used in the far-infrared frequency domain, far from the optical regime. The three-dimensional model is presented to demonstrate the ability of the structure to be integrated in photonic circuits. Then, we show that the interaction between several stubs produces a widening of the zeros of transmission into bandgaps. Inserting an appropriate defect stub between a set of periodical stubs leads to a tunneling transmission, with a narrow peak inside the gap which can be useful for selective filtering. This filtering phenomenon is used to propose a demultiplexer based on a Y-shaped waveguide for separating signals with different frequencies. Finally, we show that the filtering effect of a stub can also be reproduced when the metal is described in the framework of a Drude model instead of being perfect, which makes the realization of the above devices in the near-optical regime plausible.

The interface response theory was presented for any composite material in discrete, continuous, and mixed (partly discrete \textendash partly continuous) spaces (see Chapter 1 of Phononics in Interface Transmission Tutorial Book Series). The aim of this chapter is to show how this theory can be used for solving the Maxwell equations in any composite dielectric material. General expressions for the corresponding response functions are given. These results are illustrated by a general application to layered isotropic dielectrics and in particular simple derivations of the response functions for two media separated by an interface, for one dielectric slab sandwiched between two different semiinfinite dielectrics and for an infinite and a semiinfinite layered photonic crystals. The knowledge of the response functions enables us to study all the electromagnetic properties of these different systems. Some applications are given here for the sandwich photons (localized photons within the slab), bulk electromagnetic band for the infinite layered photonic crystal, and localized modes in semiinfinite layered photonic crystal.

Closed loops with finite open loops attached to the robust zeros of one of their two twin states are the systems investigated in this chapter. Such attached finite loops are called stubs. For simplicity, here only the cases where all the stubs have the same length are considered. This length is chosen to be commensurable with the closed loop length. So the interface points of such systems remain robust zeros for many eigenfunctions of the final systems. As a consequence, the corresponding eigenwavelengths are robust. All the states of such systems are obtained with particular attention to the path ones. An eigenfunction zero is robust because its eigenstate cannot be activated by any action applied on it. The path states are robust because they are confined within one-dimensional paths, and when they are degenerate they can turn around defects. Multiplexer and wide reflection band applications of such systems are presented. It is shown that some path states can be transferred from one infinite line to another without any perturbation. Such single wavelength transfers are of infinite quality. It is possible to transform them into finite-width resonances just by tuning the stub lengths.

Any open and closed loop eigenfunction has zero motion space points, called here robust zeros. Any such zero is robust because its eigenstate cannot be activated by any action applied on it. Indeed, such zero space positions remain unaffected when the loop is interfaced with its outside world only through one or several such robust zeros. The corresponding eigenwavelengths and eigenfunctions remain also unaffected by such interfacing. When this interfacing introduces one or several new pathways whose lengths are commensurable with the unaffected eigenwavelength, the eigenstate becomes degenerate or more degenerate. Such states remain strictly confined within an ensemble of open or closed loop paths. A confined state is strictly confined in its space subdomain. So path states belong to a subset of confined states. They are confined within combinations of open and closed loops. In such an interfacing process, the other eigenvalues shift. They may have in general more complicated eigenfunctions. Similar considerations can be developed for any system state and lead to a confined state theorem. This enables also to propose a construction method of systems with confined states. This construction method is developed in what follows for path states. They are the simplest ones, as being confined along loop paths. When the path states are degenerate, their paths can go around defects. The path states are robust because they are confined within one-dimensional paths, and when they are degenerate they can turn around defects. This chapter presents also general eigenfunction rules. These rules are mainly eigenfunction continuities and outgoing source forces equal to zero, at each network point. The source forces are for electromagnetic waves, the outgoing derivatives of the wave electric and magnetic fields. For other types of waves, the source forces are, for example, the outgoing stresses, currents, etc. These new tutorial results are illustrated by simple examples. All this can lead to a construction procedure of robust transmission lines. The confined path states can pave the way for the future of information communication technology and contribute to many other sciences.

We present simulations on both the optical properties and the efficiency of nanowires (NWs), nanopillars (NPs) and nanocones (NCs) silicon-based solar cells, together with measurements on their associated optical absorption. We address the calculation using Green's function formalism and Finite Difference Time Domain (FDTD) method, well-adapted to deal with a periodic set of nanostructures. We study the effect of the period, the bottom diameter, the top diameter, and the height of the NPs or NCs on the efficiency, assuming that one absorbed photon induces one exciton. We give general trends of the involved geometrical parameters with regard to the efficiency of the nanostructures' solar cell. Moreover, nanostructures have been processed and allow comparing experimental results with simulations. In every case, a good agreement has been found.

A closed loop can be obtained by linear superposition of the two free ends of an open loop. Its main property is the double degeneracy of its states. The analytical expressions of its eigenvalues, eigenfunctions, and response function are presented. The case of two simultaneous identical measures at two different points of a closed loop is briefly addressed. The simultaneous activation of these two degenerate states is presented from the theoretical and experimental points of view.

International audience; Improved performance in flexible organic light-emitting diodes (OLEDs) is demonstrated by using a hybrid nanostructured plasmonic electrode consisting of silver nanowires (AgNWs) decorated with silver nanoparticles (AgNPs) and covered by exfoliated graphene sheets. Such all-solution processed electrodes show high optical transparency and electrical conductivity. When integrated in an OLED with super yellow polyphenylene vinylene as the emissive layer, the plasmon coupling of the NW-NP hybrid plasmonic system is found to significantly enhance the fluorescence, demonstrated by both simulations and photoluminescence measurements, leading to a current efficiency of 11.61 cd A−1 and a maximum luminance of 20 008 cd m−2 in OLEDs. Stress studies reveal a superior mechanical flexibility to the commercial indium-tin-oxide (ITO) counterparts, due to the incorporation of exfoliated graphene sheets. Our results show that these hybrid nanostructured plasmonic electrodes can be applied as an effective alternative to ITO for use in high-performance flexible OLEDs.

International audience; We describe a computational approach to study the acousto-plasmonic coupling in metallic nanoparticles. We use the high level multiphysics finite element software FreeFEM developed at Laboratoire Jacques-Louis Lions of Pierre and Marie Curie University (Paris). Our numerical method determines one after the other the acoustic modes of the nanoparticles and the modulation of the electromagnetic properties. The transfer of the deformed geometries between acoustic and electromagnetic simulations is realized by an update of the nodal coordinates situated at the boundary between the nanoparticle and its host medium, and using a mesh deformation algorithm based on radial basis function interpolation. Thus we theoretically investigate different coupling mechanisms between confined vibrations and surface plasmons: shape effect, electron density effect due to changes of the nanoparticle volume and inter-band transitions effect which is evaluated by the deformation potential mechanism.

International audience; Matrix-free polymer grafted nanoparticles (NPs) are single component polymer nanocomposites (PNCs) for which the often reported severe aggregation of the conventional PNCs can be suppressed. For a given particle core, the size and shape of the polymer grafted nanoparticles can be controlled by the molecular weight of the polymer and its grafting density. However, the degree of homogeneity of one-component PNCs depends on the grafted chain molecular weight and grafting density, as well as on the shape of grafted NPs. Surface plasmon resonance enhanced dynamic light scattering from very dilute solutions, yielding both translational and rotational transport coefficients, complemented by UV-Vis extinction spectra, can detect deviations from spheres. Here, we report that poly(isobutylene)-grafted Ag NPs strongly deviate from the spherical shape and are modeled as prolate spheroids. This NP asphericity, due to inhomogeneous grafting, can impact the structure and properties of plasmonic PNCs in the solid state. Thus, characterizing this behavior is a crucial step prior to the formation of one-component PNCs.

International audience; This study aims to investigate the potential of small densely packed tilted Au nanorods grown on a flexible substrate by physical vapor deposition for strain sensing. By exciting the rods with linearly polarized white light that is perpendicularly impinging onto the sample substrate, interesting plasmonic properties emerge. Electron microscopy characterization shows that the rods are grown at a shallow angle relative to the substrate, as expected for glancing angle deposition conditions. Due to their nonorthogonal orientation, specific coupled multirod plasmon modes are detected for both longitudinal and transverse illumination under illumination normal to the substrate. In a second step, we have performed in situ mechanical tests and showed higher sensitivity to the applied strain for longitudinal E-field directions, which are more strongly affected by changes in inter-rod gaps than for transverse illumination. What is remarkable is that, despite the inherent disorder to this self-assembled system, clear features like polarization dependency and localized surface plasmon resonance (LSPR) wavelength shift with applied strains may be observed due to local changes in the nanorods’ environment. These nanorod coated flexible substrates rank among the most sensitive plasmonic strain sensors in the literature and have potential to be embedded in real strain sensing devices.

International audience; A significant enhancement in ultraviolet (UV) durable indium tin oxide (ITO)‐free flexible nonfullerene organic solar cells (OSCs) has been demonstrated using a hybrid nanostructured flexible transparent electrode (FTE), comprising a mixture of 0D silver nanoparticles (AgNPs), 1D Ag nanowires (AgNWs) and 2D exfoliated graphene sheets. The FTE possesses high optical transparency and electric conductivity, good air stability and full‐solution fabrication capability at a low processing temperature. An average power convention efficiency (PCE) of 8.15% has been obtained for the flexible nonfullerene OSCs, based on the blend of poly[(2,6‐(4, 8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)‐benzo[1,2‐b:4,5‐b’]dithiophene))‐alt‐(5,5‐(1’,3’‐di‐2‐thienyl‐5’,7’‐bis(2‐ethylhexyl)benzo[1’,2’‐c:4’,5’‐c’] dithiophene‐4,8‐dione)] (PBDB‐T): 3,9‐ bis(2‐methylene‐(3‐(1,1‐dicyanomethylene)‐indanone))‐5,5,11,11‐tetrakis(4‐hexylphenyl)‐dithieno[2,3‐d:2’,3’‐d’]‐s‐indaceno[1,2‐b:5,6‐b’] dithiophene (ITIC). The flexible PBDB‐T:ITIC OSCs exhibit an excellent UV durability compared to the ITO‐based control cell, realized by incorporating a FTE with a tailored absorption in wavelength < 380 nm. The novel FTE developed in this work provides a promising alternative to ITO for use in UV durable flexible OSCs, serving as a built‐in UV filter to impede an inevitable UV‐induced degradation in ITO‐based OSCs.

International audience; he dispersion of mechanical vibration limits nano-optomechanical modulation. In this work, we propose an optomechanical modulation exploiting elastic local resonances, also called whispering-gallery modes (WGMs). We find that our structure supports two quadripolar and two hexapolar elastic WGMs, which are nondispersive to avoid losses where the displacement field is localized on the gold nanodisks (AuNDs). We numerically demonstrate that the coupling between localized surface plasmon resonance (LSPR) and WGMs are relative both to the symmetry displacement of the elastic modes and to the strong isolation of phononic modes in the AuNDs. The amplitude of the modulation is evaluated by computing the wavelength shift of dipolar LSPR under different deformations by four WGMs. A detailed comparison between the four WGMs allows us to determine the ones with more efficient coupling. Furthermore, this simultaneous confinement gives a large acousto-plasmonic coupling that can be used to design a new mechanical sensor with the plasmonic response as a potential application and innovation toward new acousto-plasmonic devices.

Second-harmonic generation (SHG) is investigated from three kinds of lithographically fabricated plasmonic systems: Al monomers, Au monomers and Au-Al heterodimers with nanogaps of 20 nm. Spectrally integrated SHG intensities and the linear optical responses are recorded and compared. The results show that for the monomer nanoantennas, the SHG signal depends sensitively on the linear excitation of the plasmon resonance by the fundamental wavelength. For Au-Al heterodimer nanoantennas, apart from fundamental resonant excitation, nonlinear optical factors such as SH driving fields and phase interferences need to be taken into account, which play significant roles at the excitation and scattering stages of SHG radiation. It is interesting to note that a possible energy transfer process could take place between the two constituting nanoparticles (NPs) in the Au-Al heterodimers. Excited at the linear plasmon resonance, the Au NP transfers the absorbed energy from the fundamental field to the nearby Al NP, which efficiently scatters SHG to the far-field, giving rise to an enhanced SHG intensity. The mechanisms reported here provide new approaches to boost the far-field SHG radiation by taking full advantage of strongly coupled plasmonic oscillations and the synergism from materials of different compositions.

Here, we demonstrate a simple top-down method for nanotechnology whereby electron beam (ebeam) lithography can be combined with tilted, rotated thermal evaporation to control the topography and size of an assortment of metallic objects at the nanometre scale. In order to do this, the evaporation tilt angle is varied between 1 and 24°. The technique allows the 3-dimensional tailoring of a range of metallic object shapes from sharp, flat bottomed spikes to hollow cylinders and rings—all of which have rotational symmetry and whose critical dimensions are much smaller than the lithographic feature size. The lithographic feature size is varied from 400 nm down to 40 nm. The nanostructures are characterized using electron microscopy techniques—the specific shape can be predicted using topographic modelling of the deposition. Although individual nanostructures are studied here, the idea can easily be extended to fabricate arrays for e.g. photonics and metamaterials. Being a generic technique—depending on easily controlled lithographic and evaporation parameters—it can be readily incorporated into any standard planar process and could be adapted to suit other thin-film materials deposited using physical means.

We investigate spatiotemporal chaos dynamics in a finite nanoparticles array with Kerr-type nonlinear response, excited by an incident plane wave of varying intensity and tunable frequency close to the localized plasmon resonance of a single particle. Considering dipole-dipole coupling between the nanoparticles described by their polarizability, we compute the temporal evolution of the dipoles and numerically extract the Lyapunov spectra, allowing us to characterize different dynamical behaviors. Furthermore, we estimate the Kaplan-Yorke dimension that provides a measure of the strange attractor complexity. We show that time-modulated solutions which are generated at the onset of modulational instability experience secondary instabilities leading to a complex nonlinear dynamic. It is also shown that in the highly nonlinear regime, the spatiotemporal chaos is robust and exists in a large range of parameters that we have determined numerically.

The regular arrangement of metal nanoparticles influences their plasmonic behavior. It has been previously demonstrated that the coupling between diffracted waves and plasmon modes can give rise to extremely narrow plasmon resonances. This is the case when the single-particle localized surface plasmon resonance (λ LSP) is very close in value to the Rayleigh anomaly wavelength (λ RA) of the nanoparticles array. In this paper, we performed angle-resolved extinction measurements on a 2D array of gold nano-cylinders designed to fulfil the condition λ RA<λ LSP. Varying the angle of excitation offers a unique possibility to finely modify the value of λ RA, thus gradually approaching the condition of coupling between diffracted waves and plasmon modes. The experimental observation of a collective dipolar resonance has been interpreted by exploiting a simplified model based on the coupling of evanescent diffracted waves with plasmon modes. Among other plasmon modes, the measurement technique has also evidenced and allowed the study of a vertical plasmon mode, only visible in TM polarization at off-normal excitation incidence. The results of numerical simulations, based on the periodic Green’s tensor formalism, match well with the experimental transmission spectra and show fine details that could go unnoticed by considering only experimental data.

International audience; In order to evaluate the optical efficiency of tip-based probes for future tip-enhanced optical spectroscopy applications, we developed an experimental setup based on the coupling of an achromatic inverted microscope equipped with a total internal reflection objective and an atomic force microscopy (AFM) head. This spectroscopic tool has been validated using individual nanofabricated antennas (gold nanodisks/nanocones) on a glass substrate which act as nanoresonators based on localized surface plasmons. Spectrally tunable transverse electric and magnetic plasmonic resonances are identified and are in excellent agreement with numerical calculations performed as a function of the nanoantenna geometry and size. We investigated a series of state-of-the-art gold-coated AFM probes, which are commonly used for tip-enhanced (Raman spectroscopy) optical experiments. Their scattering spectrum consists of resonances depending on the tip sharpness or granularity superimposed on a broad emission spectrum due to a semi-infinite metal layer acting as a nonresonant antenna. From the comparison between the plasmonic response of both types of optical antennas, a new generation of probes for tip-enhanced optical spectroscopy is proposed in which single plasmonic nanoantennas are engineered at the apex of a nonmetallic AFM tip. As from numerical simulation results, such tips would ensure a spectral tunability as a function of the material, size, and geometry, together with expected high enhancement factors. Such features would allow the design of spectrally tunable surface-enhanced Raman spectroscopy substrates and should be a reliable and efficient alternative to tips commonly used in tip-enhanced optical spectroscopy experiments such as tip-enhanced Raman spectroscopy.

This chapter presents two simple models of magnons in centered systems. The first model represents N, with N ≥ 2, electron spins pointing in the same space direction and situated at different space positions. The first of these spins is in the center of a circle. The others are on this circle and are the surface of this system. This model uses the Heisenberg interaction Hamiltonian. The second model uses the long-wavelength approximation of this Hamiltonian. These models present degenerate resonant subsystem states, localized each on two of the N-1 system constituents. They show also trapping, isolation effects, degenerate surface mode behaviors, and so on. A transposition of magnons to phonons is presented then, as an example of how these excitation models are similar. Such transpositions are one of the aim of this interface transmission book series. Some general perspectives are finally given: bound in continuum states, model tuning, breaking symmetry effects, possible transpositions to other waves: plasmons, electrons, photons, polaritons, and so on.

International audience; Interest in graphene has been widely increasing since its discovery in 2004. Research on graphene for plasmonic applications has also boomed due to the high potential of these systems. In this article, we discuss the possible interaction between metallic NPs and graphene monolayer. We show how the contact between metallic NPs and graphene results in graphene doping. More importantly, we experimentally put into evidence the possible modulation of the plasmonic resonance of NPs by graphene doping. Understanding and evidencing this interaction is highly important both from a fundamental point of view and for specific applications such as active plasmonic devices.

The refractive-index sensitivity of metallic nanoparticles was investigated numerically using the FDTD method as well as analytically. The obtained results show that the sensitivity of nanoparticles situated in a homogeneous host matrix is independent of their shape. Moreover, it exclusively depends on the LSPR band location, the dielectric function of the metal constituting the nanoparticles, and the refractive index of the host matrix. In the case of nanoparticles deposited on a substrate or in close interaction with it, the sensitivity is however dependent on the shape. Additionally, a loss of sensitivity is observed. Different theoretical trails are examined in order to better understand those phenomena. The study emphasizes that the shape-dependent sensitivity can be related to the modification of the depolarization factors of the nanoparticles in the presence of a substrate.

In this chapter, we discuss the vibrational properties of phononic circuits that can be described in the framework of discrete or continuous models. In the case of discrete media, we use the phonon discrete model within the Green’s function method described in Chapter 1 and give the surface response operators necessary to study surface and confined phonons in biatomic and triatomic phononic crystals. In particular, we give a general rule about the existence of two types of discrete modes in finite and semiinfinite crystals. Also, we present a simple multiplexing phonon structure made out of two parallel mono-atomic chains of atoms and of a simple coupling device made out of two other atoms interacting together and with the two chains. We show analytically that these simple structures can transfer selectively along a given path, one phonon from one chain to the other leaving neighbor phonons unaffected. In the case of continuous media, we consider simple acoustic devices consisting of attached resonators in the shape of stubs and loops tubes inserted along a slender tube. These structures can be arranged from very simple structures (two resonators) mimicking the classical analog of Fano and electromagnetic induced transparency resonances, to periodic structures showing the possibility of existence of Bragg and non-Bragg gaps, to quasiperiodic (Fibonacci sequence) structures exhibiting some transmission scaling properties of such systems.

This chapter is on phonons in supported slabs. It starts by a presentation of the general equations for an elastic material. General analytic expressions are obtained for bulk and surface Green’s functions, as simple examples of the continuous interface response theory of Chapter 1 of this book. With the same coherent approach, many analytical results are presented for resonant guided elastic waves in an adsorbed slab and in an adsorbed bilayer on homogenous substrates. The case of an adsorbed layer on a one-dimensional phononic crystal is also considered. Finally the relation of these results with some experiments, such as Raman and Brillouin light scattering, are discussed.

In this chapter, we discuss the vibrational properties of one-dimensional (1D) phononic crystals of both discrete and continuous media. These properties include the dispersion curves of infinite crystals as well as the confined modes and localized (surface, cavity) modes of finite and semi-infinite crystals. A general rule about the existence of localized surface modes in finite and semi-infinite superlattices with free surfaces is presented. We also present the calculations of reflection and transmission coefficients, particularly in view of selective filtering through localized modes. Most of the results presented in this chapter deal with waves propagating along the axis of the superlattice. However, in the last part of the chapter, we also discuss wave propagation out of the normal incidence and, more particularly, we demonstrate the possibility of omnidirectional transmission gap and selective filtering for any incidence angle. A comparison of the theoretical results with experimental data available in the literature is also presented and the reliability of the theoretical predictions is indicated.

In this chapter we describe the basic concepts of two-dimensional (2D) phononic crystals. We start with a detailed presentation of the elementary methods for the calculation of band structures and transmission phenomena which have proven their efficiency in the literature. We respectively present the plane wave expansion method, the finite difference time domain method, and the finite element method and discuss their respective advantages or drawbacks for different purposes and their applications to some current structures. The main objective is to give the elementary ingredients for graduated students to start the phononic crystal topic from the beginning. Beside we apply the methods to 2D infinite phononic crystals and show the condition of band gap existence as a function of the geometrical and physical parameters. Band gap maps of 2D phononic crystals have been presented by means of dispersion curve calculations. We then turn to the calculation of the transmission and present applications that can be easily reproduced, as the manipulation of acoustic waves through linear or point defect and to sensing applications. At lower frequencies, we present examples of low resonant sonic materials that were at the origin of the acoustic metamaterial (AMM) field introduced by P. Sheng in 2000. For AMMs, the driving wavelength is at least one order of magnitude higher than every dimension of the constitutive elements. We then present systematically the main physical properties of band gaps for different finite thickness 2D phononic crystal plates and discuss the condition of existence of the band gap for two kinds of phononic plates. The first one is a membrane drilled with air holes. The second one is made of pillar deposited on a thin membrane. The last structure opens the way to low frequency band gap that can be compared to low resonant sonic materials and now cover the field of AMMs.

A general theory of interface response in linear composite systems is presented in the first chapter of this book on phononics. Specific examples, fully developed in the next chapters of this book, are shortly presented in this chapter. Other examples using this general interface response theory appear also in the following books of this interface transmission tutorial book series. This theory is first presented for discrete systems with a matrix mathematical formulation. Then the case of continuous systems described by differential equations is given. In this case the response functions are the classical Green’s functions. Finally the case of partly discrete and partly continuous composite systems is also discussed.

In this contribution, a numerical study of the optical properties of closely-packed gold nanorods was performed. The studied nano-objects are experimentally grown on a tilted polydimethylsiloxane (PDMS) substrate by using physical vapor deposition (PVD). This method creates nanorods tilted to a certain angle with respect to the substrate normal. This geometry allows exciting both transverse and longitudinal modes of the rods. As demonstrated in a previous experimental work, such PVD-grown nano-objects show promising possibilities both as strain gauges or strain-tunable metamaterials if fabricated on a stretchable dielectric substrate. This numerical study is based on experimental data from previous work and pushes further the subject by approaching an optimized nano-structure allowing better strain-sensitivity (particularly by changing the auto-organization of the said nanorods). Full Text: PDF References J.W.M. Chon, C. Bullen, P. Zijlstra, M. Gu, "Spectral encoding on Gold Nanorods Doped in a Silica Sol?Gel Matrix and Its Application to High-Density Optical Data Storage", Adv. Funct. Mater. 17, 875 (2007). CrossRef C.-C. Chen, Y.-P. Lin, C.-W. Wang, H.-C. Tzeng, C.-H. Wu, Y.-C. Chen, C.-P. Chen, L.-C. Chen, Y.-C. Wu, "DNA?Gold Nanorod Conjugates for Remote Control of Localized Gene Expression by near Infrared Irradiation", J. Am. Chem. Soc. 128, 3709 (2006). CrossRef J.N. Anker, W.P. Hall, O. Lyandres, N.C. Shah, J. Zhao, R.P. Van Duyne, "Biosensing with plasmonic nanosensors", Nat. Mater 7, 442 (2008). CrossRef B. Sepulveda, P.C. Angelome, L.M. Lechuga, L.M. Liz-Marzan?, "LSPR-based nanobiosensors", Nano Today 4, 244 (2009). CrossRef A. Haes, R.P. Van Duyne, "A Nanoscale Optical Biosensor: Sensitivity and Selectivity of an Approach Based on the Localized Surface Plasmon Resonance Spectroscopy of Triangular Silver Nanoparticles", J. Am. Chem. Soc. 124, 10596 (2002). CrossRef J.C. Riboh, A.J. Haes, A.D. McFarland, C.R. Yonzon, R.P. Van Duyne, "A Nanoscale Optical Biosensor: Real-Time Immunoassay in Physiological Buffer Enabled by Improved Nanoparticle Adhesion", J. Phys. Chem. B 107, 1772 (2003). CrossRef C.R. Yonzon, E. Jeoung, S. Zou, G.C. Schatz, M. Mrksich, R.P. Van Duyne, "A Comparative Analysis of Localized and Propagating Surface Plasmon Resonance Sensors: The Binding of Concanavalin A to a Monosaccharide Functionalized Self-Assembled Monolayer", J. Am. Chem. Soc. 126, 12669 (2004). CrossRef A.J. Haes, L. Chang, W.L. Klein, R.P. Van Duyne, "Detection of a Biomarker for Alzheimer's Disease from Synthetic and Clinical Samples Using a Nanoscale Optical Biosensor", J. Am. Chem. Soc. 127, 2264 (2005). CrossRef R. Caputo, G. Palermo, M.Infusino L. De Sio, "Liquid Crystals as an Active Medium: Novel Possibilities in Plasmonics", Nanospectroscopy 1, 40 (2015). CrossRef T. Maurer, J. Marae-Djouda, U. Cataldi, A. Gontier, G. Montay, Y. Madi, B. Panicaud, D. Macias, P.-M. Adam, G. Lev?que, T. Burgi, R. Caputo, "The beginnings of plasmomechanics: towards plasmonic strain sensors", Frontiers of Materials Science 9, 170 (2015). CrossRef X. Niu, S. P. Stagon, H. Huang, J.K. Baldwin, A. Misra, "Smallest Metallic Nanorods Using Physical Vapor Deposition", Phys. Rev. Lett. 110 136102 (2013). CrossRef Lumerical Solutions, Inc. DirectLink P.K. Jain, W. Huang, M.A.El-Sayed, "On the Universal Scaling Behavior of the Distance Decay of Plasmon Coupling in Metal Nanoparticle Pairs: A Plasmon Ruler Equation", Nanoletters 7, 2080 (2007). CrossRef P.K. Jain, M.A. El-Sayed, "Plasmonic coupling in noble metal nanostructures", Chem. Phys. Letters 487, 153 (2010). CrossRef

The sensitivity of the wavelength position of localized surface plasmon resonance (LSPR) in metal nanostructures to local changes in the refractive index has been widely used for label-free detection strategies. Tuning the optical properties of the nanostructures from the visible to the infrared region is expected to have a drastic effect on the refractive index sensitivity. Here, we theoretically investigate the optical response of a newly designed plasmonic interface to changes in the bulk refractive index by the finite difference time domain method. It consists of a structured interface, where the planar interface is superposed with dielectric pillars 30 nm in height and 125 nm in length with a separation distance of 15 nm. The pillars are covered with U-shaped gold nanostructures of 50 nm in height, 125 nm in length, and 5 nm of gold base thickness. The whole structure is finally covered with a 5-nm thick dielectric layer of n2 = 2.63. This plasmonic structure shows bulk refractive index sensitivities up to 1750 nm/RIU (RIU : refractive index unit) in the near infrared (λ = 2621 nm). The enhanced sensitivity is a consequence of the extremely enhanced electrical field between the gold nanopillars of the plasmonic interface.

International audience; We study theoretically and numerically bidimensional square gratings of monomers and dimers of gold nanocylinders supported on a dielectric substrate, under plane wave illumination as a function of the angle of incidence and of the polarization. The number of parameters investigated makes that system a rich platform for the investigation of how grating coupling, and in particular edge diffraction which corresponds to the grazing propagation of a particular diffracted order, influence the surface plasmons response of nanoparticles. In particular, the considered periods are comparable to the range of incident wavelength, which makes the interpretation of the observed phenomena complex due to the large number of diffraction orders coming into play. In order to analyze those systems, we perform exact numerical simulations using Green’s tensor method, and compare them to a simplified approach based on the coupled-dipole approximation. The systematic identification of the grazing diffracted orders, combined with the computation of the S-matrix components, leads to better understanding of the different types of profiles (sharp maxima or angular minima) observed in the extinction spectra around the Rayleigh wavelengths associated with grazing diffraction in air or glass. The analysis is supported by computation of several electric field distributions computed for selected parameters.

International audience; We investigate theoretically and numerically the coupling between elastic and localized surface plasmon modes in a system of gold nanocylinders separated from a thin gold film by a dielectric spacer of few nanometers thickness. That system supports plasmon modes confined in between the bottom of the nanocylinder and the top of the gold film, which arise from the formation of interference patterns by short-wavelength metal-insulator-metal propagating plasmon. First, we present the plasmonic properties of the system though computer-simulated extinction spectra and field maps associated to the different optical modes. Next, a simple analytical model is introduced, which allows to correctly reproduce the shape and wavelengths of the plasmon modes. This model is used to investigate the efficiency of the coupling between an elastic deformation and the plasmonic modes. In the last part of the paper, we present the full numerical simulations of the elastic properties of the system, and then compute the acousto-plasmonic coupling between the different plasmon modes and five acoustic modes of very different shape. The efficiency of the coupling is assessed first by evaluating the modulation of the resonance wavelength, which allows comparison with the analytical model, and finally in term of time-modulation of the transmission spectra on the full visible range, computed for realistic values of the deformation of the nanoparticle.

Amplitude and phase measurements of the near-field generated by isolated subwavelength apertures in a gold film are presented. The near-field distribution of such a structure is complex and the measured signal strongly depends on the electric field components effectively detected by the experimental setup. By comparing this signal with 3D vectorial calculations we are able to determine which electric field components are effectively measured. The sensitivity of the phase distribution is key to this measurement. The proposed characterization technique should prove extremely useful to calibrate a Scanning near-field optical microscopy (SNOM) beforehand in order to retrieve quantitative information on the polarization of the field distribution under study.