Localized Surface Plasmon Polaritons Research Articles

Numerical investigation of optical Tamm states in two-dimensional hybrid plasmonic-photonic crystal nanobeams

Optical Tamm states (OTSs) in analogy with its electronic counterpart confined at the surface of crystals are optical surface modes at the interfaces between uniform metallic films and distributed Bragg reflectors. In this paper, OTSs are numerically investigated in two-dimensional hybrid plasmonic-photonic crystal nanobeams (HPPCN), which are constructed by inserting a metallic nanoparticle into a photonic crystal nanobeam formed by periodically etching square air holes into dielectric waveguides. The evidences of OTSs can be verified by transmission spectra and the field distribution at resonant frequency. Similar to OTSs in one-dimensional multilayer structures OTSs in HPPCN can be excited by both TE and TM polarization. The physical origin of OTSs in HPPCN is due to the combined contribution of strong reflection imposed by the photonic band gap (PBG) of the photonic crystal (PC) nanobeam and strong backward scattering exerted by the nanoparticle. For TE, incidence OTSs can be obtained at the frequency near the center of the photonic band gap. The transmissivity and the resonant frequency can be finely tuned by the dimension of nanoparticles. While for TM incidence OTSs are observed for relatively larger metallic nanoparticles compared with TE polarization. The differences between TE and TM polarization can be explained by two reasons. For one reason stronger backward scattering of nanoparticles for TE polarization can be achieved by the excitation of localized surface plasmon polariton of nanoparticles. This assumption has been proved by examining the scattering, absorption, and extinction cross section of the metallic nanoparticle. The other can be attributed to the deep and wide PBG available for TE polarization with less number of air holes compared with TM polarization. Our results show great promise in extending the application scope of OTSs from one-dimensional structures to practical integrated photonic devices and circuits.

The coupling of angular momentum of light in metal triangles nano-ring

In this paper, we proposed that local field intensity can be further enhanced by using the light beam carrying the angular momentum to excite the surface plasmon polariton (SPP). The physical process of interaction between the beam carrying the different angular momentum and metal triangles nano-ring(MTNR) and the local SPP enhancement effect are discussed in detail. When the angular momentum of light beam match well with MTNR structure, local electric field will be further enhanced, which provide an effective way to enhanced the localized surface plasmon polaritons (LSPPs). We finally fabricated the MTNR by using microspheres self-assembly and vacuum depositing method and give a proposal experiment to verify the further enhancement of LSPP based on exciting light beam carrying angular momentums.

Plasmon scattering from holes: from single hole scattering to Young’s experiment

In this paper, the scattering of surface plasmon polaritons (SPPs) into photons at holes is investigated. A local, electrically excited source of SPPs using a scanning tunneling microscope (STM) produces an outgoing circular plasmon wave on a thick (200 nm) gold film on glass containing holes of 250, 500 and 1000 nm diameter. Fourier plane images of the photons from hole-scattered plasmons show that the larger the hole diameter, the more directional the scattered radiation. These results are confirmed by a model where the hole is considered as a distribution of horizontal dipoles whose relative amplitudes, directions, and phases depend linearly on the local SPP electric field. An SPP-Young’s experiment is also performed, where the STM-excited SPP wave is incident on a pair of 1 μm diameter holes in the thick gold film. The visibility of the resulting fringes in the Fourier plane is analyzed to show that the polarization of the electric field is maintained when SPPs scatter into photons. From this SPP-Young’s experiment, an upper bound of ≈200 nm for the radius of this STM-excited source of surface plasmon polaritons is determined.

Dual-band infrared perfect absorber based on asymmetric T-shaped plasmonic array.

An infrared dual-band perfect absorber based on asymmetric T-shaped plasmonic array is designed and numerically investigated. Two distinct absorption peaks are achieved by localized surface plasmon polariton (LSPP) mode over a wide incident angular range. Both the absorption peaks can be finely tuned independently by varying the geometry of the structure. In our proposed structure, the period of the T-shaped structures becomes less and the multiple LSPP peaks are suppressed, which result in the sideband of absorption peaks very low. This dual-band perfect absorber has potential applications such as in infrared imaging devices, thermal bolometers, and wavelength selective radiators.

Electromagnetic interaction between local surface plasmon polaritons and an atmospheric surface wave plasma jet

We analyze the electromagnetic interaction between local surface plasmon polaritons (SPPs) and an atmospheric surface wave plasma jet (ASWPJ) in combination with our designed discharge device. Before discharge, the excitation of the SPPs and the spatial distribution of the enhanced electric field are analyzed. During discharge, the critical breakdown electric field of the gases at atmospheric gas pressure and the surface wave of the SPPs converted into electron plasma waves at resonant points are studied. After discharge, the ionization development process of the ASWPJ is simulated using a two-dimensional fluid model. Our results suggest that the local enhanced electric field of SPPs is merely the precondition of gas breakdown, and the key mechanism in maintaining the discharge development of a low-power ASWPJ is the wave-mode conversion of the local enhanced electric field at the resonant point.

Tailoring of quantum dot emission efficiency by localized surface plasmon polaritons in self-organized mesoscopic rings

We report on the tailoring of quantum dot (QD) emission efficiency by localized surface plasmon polaritons in self-organized mesoscopic rings. Ag nanoparticles (NPs) with CdSe QDs embedded in a polymeric matrix are spatially organised in mesoscopic rings and coupled in a tuneable fashion by breath figure formation. The mean distance between NPs and QDs and consequently the intensity of QD photoluminescence, which is enhanced by the coupling of surface plasmons and excitons, are tuned by acting on the NP concentration.

Sensitive surface-enhanced Raman scattering active substrate based on gap surface plasmon polaritons

The authors fabricate three types of surface-enhanced Raman scattering (SERS) active substrates by nanoimprint lithography and experimentally investigated the intensity enhancement of Raman scattering induced by gap surface plasmon polaritons (GSPPs). An area-averaged Raman signal enhancement factor of 1.1 × 107 can be achieved by the GSPPs structures for monolayer thiophenol molecules absorbed on silver surfaces, compared with 6.2 × 105 of conventional SERS-active substrates. The exceptional field enhancement originates not only from the localized surface plasmon polaritons but also from the coupling between the GSPPs at two metal/dielectric interfaces. These structures are expected to find promising applications as SERS devices in trace-level molecular detection and identification.

Enhanced photoluminescence emission from anthracene-doped polyphenylsiloxane glass

Anthracene-doped polyphenylsiloxane (PPS) glass containing silver nanoparticles (AgNPs) of appropriate size was synthesized in a form of solid thin films for modifying light emission characteristics. The photoluminescence (PL) emission from the anthracene molecules at ~2.95 eV was resonantly coupled to the localized surface plasmon (LSP) polariton modes that were induced by the excitation of ~30 nm sized AgNPs. The increase in absorption of incident photons within a highly scattering medium, energy transfer from the localized excitons to the LSP modes, and the electrostatic Coulomb effects of the excitons in the presence of metal NPs all resulted in a significant enhancement of PL emission. The PL enhancement is dependent on the concentration of the anthracene molecules. The integrated PL intensity enhancement at the optimum concentration of anthracene molecules in the PPS glass with AgNPs is found to exceed 50.

Highly Sensitive Plasmonic Sensor Based on Fano Resonance from Silver Nanoparticle Heterodimer Array on a Thin Silver Film

We investigate the optical spectrum of a multilayer metallic slab using multiple-scattering formalism. A thin silver film is attached to a periodic array of heterodimers consisting of two vertically spaced silver nanoparticles of different radii. Depending on the radius of nanoparticles, heterodimer array presents a simple nanoscale geometry which gives rise to remarkable plasmonic properties of multipolar resonances. Due to the coherent interference of the localized nanoparticle plasmons (discrete mode) and surface plasmon polaritons of metallic film (continuous mode), the reflection spectrum represents a sharp asymmetric Fano resonance dip, which is strongly sensitive to the refractive index of the surrounding embedded dielectric host. The physical features contribute to a highly efficient plasmonic sensor for refractive index sensing with sensitivity of ∼1.5 × 10−3 RIU/nm.

Semiconductor plasmonic crystals: active control of THz extinction

We investigate theoretically the enhanced THz extinction by periodic arrays of semiconductor particles. Scattering particles of doped semiconductors can sustain localized surface plasmon polaritons, which can be diffractively coupled giving rise to surface lattice resonances. These resonances are characterized by a large extinction and narrow bandwidth, which can be tuned by controlling the charge carrier density in the semiconductor. The underlaying mechanism leading to this tuneability is explained using the coupled dipole approximation and considering GaAs as the semiconductor. The enhanced THz extinction in arrays of GaAs particles could be tuned in a wide range by optical pumping of charge carriers.

Plasmonic fractals: ultrabroadband light trapping in thin film solar cells by a Sierpinski nanocarpet

Plasmonic Sierpinski nanocarpet as back structure for a thin film Si solar cell is investigated. We demonstrate that ultra-broadband light trapping can be obtained by placing square metallic nanoridges with Sierpinski pattern on the back contact of the thin film solar cell. The multiple-scale plasmonic fractal structure allows excitation of localized surface plasmons and surface plasmon polaritons in multiple wavelengths leading to obvious absorption enhancements in a wide frequency range. Full wave simulations show that 109 % increase of the short-circuit current density for a 200 nm thick solar cell, is achievable by the proposed fractal back structure. The amount of light absorbed in the active region of this cell is more than that of a flat cell with semiconductor thickness of 1,000 nm.

Optical interaction in a plasmonic metallic particle chain coupled to a metallic film

We study the coupling of localized surface plasmon and surface plasmon polariton modes in a system composed of a metallic nanoparticle chain imbedded in a dielectric–metal–dielectric substrate. The results show the influence of outside parts and imbedded parts of particles on the interaction between localized surface plasmon and surface plasmon polariton modes. An enhancement can be observed in our structure. This kind of the structure has a very promising candidate for biosensing and surface enhanced spectroscopy applications.

Variational theory of soliplasmon resonances

We present a first-principles derivation of the variational equations describing the dynamics of the interaction of a spatial soliton and a surface plasmon polariton (SPP) propagating along a metal/dielectric interface. The variational ansatz is based on the existence of solutions exhibiting differentiated and spatially resolvable localized soliton and SPP components. These states, referred to as soliplasmons, can be physically understood as bound states of a soliton and a SPP. Their respective dispersion relations permit the existence of a resonant interaction between them, as pointed out in Ref.[1]. The existence of soliplasmon states and their interesting nonlinear resonant behavior has been validated already by full-vector simulations of the nonlinear Maxwell's equations, as reported in Ref.[2]. Here, we provide the theoretical demonstration of the nonlinear resonator model previously introduced in our previous work and analyze all the approximations needed to obtain it. We also provide some extensions of the model to improve its applicability.

Interaction of two plasmon modes in the organic photovoltaic devices with patterned back-electrode

We designed and fabricated silver grating structures on the back-electrodes of organic photovoltaic (OPV) devices to achieve absorption enhancement. The observed enhancement is attributed to several effects, including scattering through corrugated grating surface and surface plasmon modes generated by periodic plasmonic structure. Two plasmon modes are identified in our structure: localized surface plasmon (LSP) and surface plasmon polariton (SPP) modes. The former exists near the absorption edge of the active material and extends the absorption band while the latter provides an absorption pathway in the sub-gap region. Also, LSP is insensitive to active layer thickness and grating period, while the SPP which is excited whenever the momentum matching condition is satisfied shows strong dependence on active layer thickness and grating period. The two modes also exhibit strong interaction as indicated by anti-crossing behavior and thus the interplay between the two modes must be considered for back-electrode design.

Sensitivity enhancement of surface plasmon resonance sensor using continuous film metallic gratings

A surface plasmon resonance (SPR) sensor based on continuous film metallic gratings is numerically investigated for enhance sensitivity. The results calculated by rigorous coupled-wave analysis (RCWA) present that interplays between localized surface plasmons and surface plasmons polaritons contribute to sensitivity enhancement. The sensitivity enhancement factor (SEF), which represents the influence of metallic grating, increased as the grating period decreased. In addition, several reflection dips can be achieved as the period of metallic grating increased. By double-dips method, the sensitivity SPR sensor based on continuous film grating-based is improved into 153.23°/RIU, which is more sensitive than conventional thin film-based SPR sensor in the same condition. The SPR sensor based on continuous film metallic gratings exhibits good linearity.

Enhanced rotation of the polarization of a light beam transmitted through a silver film with an array of perforated S-shaped holes.

In this Letter, we realized an enhanced optical rotation of the zero-order transmitted light through a silver film with an array of perforated S-shaped holes. Different from the previous studies, this effect results from the contribution of both the localized surface plasmons and surface plasmon polaritons (SPPs). The rotation angle can be modulated with the thickness due to the phase retardation of the SPPs when tunneling to the emitted surface. With a sample thickness 245 nm, a near-complete cross-polarization conversion (90° optical rotation) can be achieved, representing a major advance in performance compared to the previously reported planar chiral structures.

Plasmonic photovoltaics: near-field of a metal nanowire array on the interface for solar cell efficiency enhancement

The analysis of the main principles of plasmonic photovoltaics relative to the enhancement of the efficiency of solar cells (SCs) by means of light trapping in a thin film SC is considered in this paper. Theoretical analysis and corresponding numerical calculations of the transmittance into a semiconductor base enhancement due to light trapping via the excitation of local (surface) plasmons and surface plasmon polaritons in a periodic metal nanowire array have been performed. The calculations have been performed for rectangular cross-section metal nanowires by the differential formalism method using the covariant form of Maxwell’s equations in a curvilinear coordinate system. Local distributions of the electric field in plasmonic nanostructures are calculated for metal nanowires in both s- and p-polarization of incident light. Then both the light transmittance in the near- and far-field (wave) zones and the local generation rate of electron–hole pairs have been calculated using the spatial distribution of the Poynting vector. Angular/spectral distributions of transmittance and position/spectral distributions of the generation rate in the near-field zone have complicated the non-homogeneous character due to the excitation of surface plasmons and surface plasmon polaritons. It has been shown that the main highly enhanced near-field generation is localized in the so-called hot points on the nanoparticles/nanowires surface. The planar-averaged generation rate for the p-polarization of light has a near-field component, which is always more for a Si base (indirect bandgap semiconductor) than for GaAs (direct bandgap one). This plasmonic effect can be used for the base thicknesses down up to 100–150 nm due to light scattering and the surface plasmon enhancement of near-fields. These plasmon-carrying metal nanowires can be used as a current grid in an SC too.

Polymeric photovoltaics with various metallic plasmonic nanostructures

Broadband light absorption enhancement is numerically investigated for the active light harvesting layer of an organic photovoltaic (OPV), which consists of a blend of poly(3-hexylthiophene) (P3HT) and the fullerene derivative [6,6]-phenyl-C61 butyric acid methyl ester (PCBM). Periodic plasmonic nanostructures placed above and below the active layer incorporate Ag, Al, Au, or a combination of two different metals. Three dimensional (3D) full-field electromagnetic simulations are applied to determine the effect of varying the metal employed in the plasmonic nanostructures on the absorption enhancement of the OPV. In addition, the geometric parameters (e.g., film thickness, period, and diameter) of the symmetrically distributed top and bottom metal (Ag, Al, or Au) nanostructures were varied to optimize the device structure and delineate the mechanism(s) leading to the absorption enhancement. A spectrally broadband, polarization-insensitive, and wide-angle absorption enhancement is obtained using a double plasmonic nanostructure and is attributed to the combined excitation of localized and single-interface surface plasmon polariton modes. The total photon absorption of the OPV with the optimized double plasmonic Ag nanostructures was found to be enhanced by as much as 82.8% and 80.4% under normal (0°) and 60° light incidence, respectively.

Hybrid plasmonic-photonic modes in diffractive arrays of nanoparticles coupled to light-emitting optical waveguides

We study the hybridized plasmonic-photonic modes supported by two-dimensional arrays of metallic nanoparticles coupled to light-emitting optical waveguides. Localized surface plasmon polaritons in the metallic nanoparticles can couple to guided modes in the underlying waveguide, forming quasi-guided hybrid modes, or to diffracted orders in the plane of the array, forming surface lattice resonances. We consider three kinds of samples: one sustains quasi-guided modes only, another sustains surface lattice resonances only, and a third sample sustains both modes. This third sample constitutes the first demonstration of simultaneous coupling of localized surface plasmons to guided modes and diffracted orders. The dispersive properties of the modes in the samples are investigated through light extinction and emission spectroscopy. We elucidate the conditions that lead to the coexistence of surface lattice resonances and quasi-guided hybrid modes, and assess their potential for enhancing the luminescence of emitters embedded in the coupled waveguide. We find the largest increase in emission intensity for the surface lattice resonances, reaching up to a factor of 20.

Second Harmonic Generation in Plasmonic Nanoresonators

Nonlinear effects can be enhanced and tailored on a subwavelength scale by taking advantage of high field confinement by selective coupling among resonant plasmonic nanostructures, called plasmonic nanoresonators and nanoantennas. In particular, we focus our attention on the process of second-harmonic (SH) generation. Excitation of localized surface plasmon polaritons at the fundamental frequency in these structures can remarkably modify the response of the system by enhancing surface and/or bulk nonlinear contributions to the overall SH field. Moreover, the radiation pattern of the generated field can be controlled and directed. Indeed, the overall structure behaves as a nonlinear nanoantenna for the SH harmonic field, whose emission pattern can be tailored.