Interference Of Surface Plasmon Polaritons Research Articles

A Generalized Methodology of Designing 3D SERS Probes with Superior Detection Limit and Uniformity by Maximizing Multiple Coupling Effects.

Accurate design of high‐performance 3D surface‐enhanced Raman scattering (SERS) probes is the desired target, which is possibly implemented with a prerequisite of quantifying formidable multiple coupling effects involved. Herein, by combining theory and experiments on 3D periodic Au/SiO2 nanogrid models, a generalized methodology of accurately designing high performance 3D SERS probes is developed. Structural symmetry, dimensions, Au roughness, and polarization are successfully correlated quantitatively to intrinsic localized electromagnetic field (EMF) enhancements by calculating surface plasmon polariton (SPP), localized surface plasmon resonance (LSPR), optical standing wave effects, and their couplings theoretically, which is experimentally verified. The hexagonal SERS probes optimized by this methodology realize over two orders of magnitudes (405 times) improvement of detection limit for Rhodamine 6G model molecules (2.17 × 10−11 m) compared to the unoptimized probes with the same number density of hot spots, an enhancement factor of 3.4 × 108, a uniformity of 5.52%, and are successfully applied to the detection of 5 × 10−11 m Hg ions in water. This unambiguously results from the Au roughness‐independent extra 144% contribution of LSPR effects excited by SPP interference waves as secondary sources, which is very unusual to be beyond the conventional recognition.

Possible deviations from AM1.5 illumination in coherent light simulations on plasmonic nanostructures in Perovskite solar cells

The use of plasmonic nanostructures for light management in solar cells has been explored for conventional materials and is currently topic of interest for the perovskite solar cell. Often these studies make use of finite difference time domain (FDTD) simulations in which high intensity coherent light is used, which simultaneously generates multiple plasmon excitations in the plasmonic nanostructures in agreement with the quantum mechanical view . However, because of the relatively small photon flux of real sun light, in the classical view only one plasmon excitation can be generated at a time in real plasmonic nanostructured devices. In this work we demonstrate that the use of high intensity coherent light in simulations causes significant optical absorption variations due to surface plasmon polariton (SPP) interference, depending on incident light phase difference between neighboring plasmonic nanostructures. Because this is not possible under real sun light conditions in the classical view, this could constrain such FDTD simulations. The question therefore arises if a quantum mechanical view is more appropriate. In this case study the plasmonic nanostructures are embedded in Perovskite, which has a strong optical absorption from silver surface plasmon polaritons and is therefore sensitive to SPP interference. This study raises the question whether to mimic real sun light, SPPs should be separately generated at each individual plasmonic nanostructure, or that the quantum mechanical view leads to a better agreement with the experimental solar cell.

Control of plasmon-polariton vortices on the surface of a metal layer.

Surface plasmon polaritons (SPPs) can be excited at the interface of a metal layer and a dielectric layer by various methods. If an inhomogeneity of permittivity with a curvilinear boundary is created in the metal layer by the external electric field, the incident SPPs and the reflected ones from this inhomogeneity interfere with one another. A nonrectangular vortex lattice appears when such SPP interference occurs, and the lattice configuration can be controlled by varying the external electric field. Based on control of the SPP vortex lattice and reading out of the vortex localization, the plasmon logic gates "AND," "OR," and "NOT" can be realized. These logic gates represent a functionally complete basis for logical operations in processors operating at optical frequencies.

Dynamic control of the interference pattern of surface plasmon polaritons and its application to particle manipulation

This study proposes a method of dynamically controlling the interference pattern of surface plasmon polaritons (SPPs) within a four-slit structure by changing the phase difference between multiple-incident Gaussian beams. The theoretical analysis of the controlling mechanism of the SPP interference field and the numerical simulation of the generation and movement of both one-dimensional and two-dimensional SPP interference fields are provided. In addition, through simulation, this study demonstrates using the controllable two-dimensional SPP interference bright spots field for manipulating particles in static liquids.

Resonance Behaviors of Localized Surface Plasmon on an Ag/GaN Nano-Grating Interface for Light-Emitting Diode Application

Although a metal grating structure is usually fabricated for momentum-matching a surface plasmon polariton (SPP) with photon, for surface plasmon (SP) coupling application in a light-emitting diode (LED), localized surface plasmon (LSP) on such a structure also plays an important role. We numerically study the LSP resonance behaviors, including the localized resonance behavior of counter-propagating SPP interference, of an Ag grating on GaN. It is found that the resonance behaviors of LSP are controlled not only by the geometry of a grating ridge, but also by grating period, particularly when the grating period is small. In a grating with sharp ridge, large ridge height or width, LSP features of dense charge distributions around the boundaries between ridges and connecting valleys exist. The spectral positions of such LSP features are weakly dependent on the ridge width. Among such features, those with their mode field oscillations across a ridge and hence distributions in an extended space around the ridge can more strongly couple with the quantum wells of an LED. Because of the short coverage range of SPP evanescent field, the localized resonance feature caused by counter-propagating SPP interference has a shorter coupling range. For LED application, an LSP mode with field oscillation across a ridge is preferred.

Formation of Surface Plasmon-Polariton Vortices at Reflection from Curvilinear Boundary

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Subfemtosecond and Nanometer Plasmon Dynamics with Photoelectron Microscopy: Theory and Efficient Simulations

We develop a theoretical model of the excitation and interference of surface plasmon polariton (SPP) waves with femtosecond laser pulses and use the model to understand the features in images from subfemtosecond time-resolved two-photon photoelectron microscopy (2PPE- PEEM). The numerically efficient model is based on the optics of SPP modes on multi-layer thin films and takes account of the excitation and interference by the incident light, its polarization, the boundary shape on the film where the plasmons are generated, the pulsed form of the excitation and the time integration associated with the PEEM method. The model explains the dominant features observed in the images including the complex patterns formed in experiments involving orbital angular momentum. The model forms the basis of an efficient numerical method for simulating time-resolved 2PPE-PEEM images of SPP wave propagation. The numerics is extremely fast, efficient and accurate, so that each image can takes as little as a few seconds to c...

2D surface optical lattice formed by plasmon polaritons with application to nanometer-scale molecular deposition

Surface plasmon polaritons, due to their tight spatial confinement and high local intensity, hold great promises in nanofabrication which is beyond the diffraction limit of conventional lithography. Here, we demonstrate theoretically the 2D surface optical lattices based on the surface plasmon polariton interference field, and the potential application to nanometer-scale molecular deposition. We present the different topologies of lattices generated by simple configurations on the substrate. By explicit theoretical derivations, we explain their formation and characteristics including field distribution, periodicity and phase dependence. We conclude that the topologies can not only possess a high stability, but also be dynamically manipulated via changing the polarization of the excitation laser. Nanometer-scale molecular deposition is simulated with these 2D lattices and discussed for improving the deposition resolution. The periodic lattice point with a width resolution of 33.2 nm can be obtained when the fullerene molecular beam is well-collimated. Our study can offer a superior alternative method to fabricate the spatially complicated 2D nanostructures, with the deposition array pitch serving as a reference standard for accurate and traceable metrology of the SI length standard.

Direction-tunable enhanced emission from a subwavelength metallic double-nanoslit structure.

Controlling light emission out of subwavelength nanoslit/aperture structures is of great important for highly integrated photonic circuits. Here we propose a new method to achieve direction-tunable emission based on a compact metallic microcavity with double nanoslit. Our method combines the principles of Young's interference and surface plasmon polaritons interference. We show that the direction of the far-field beam can be controlled over a wide range of angles by manipulating the frequency and relative phase of light arriving at the two slits, which holds promise for applications in the ultracompact optoelectronic devices.

Four-Port Polarization and Topological Charge Controlled Directional Plasmonic Coupler

In this letter, a four-port directional plasmonic coupler based on excited surface plasmon polariton interference is proposed, which is capable of coupling surface wave into different directions according to polarization directions and topological charges of incident light. In addition, it also acts as a light detector for both polarization and phase twist determination. It is believed that the directional plasmonic coupler will be potential in future plasmonic circuit designs and applications.

Vortex lattice of surface plasmon polaritons

We theoretically investigate the formation of a plasmon polariton vortex lattice on a metal surface following the interference of surface plasmon polaritons (SPPs). The plasmon polariton vortex lattice is formed by the interference of the SPP transverse-magnetic mode (TM-mode) and electric mode (E-mode) in the presence of the inhomogeneity with a curvilinear boundary on the surface of the metal layer. The SPP vortex lattice can be controlled by changing the configuration of the boundary. Weak nonlinearity of the metal permittivity does not change the interference pattern, but it increases the propagation length of the SPPs and, therefore, the area of the vortex lattice too.

Formation of vortices by interference of surface plasmon polaritons.

The TM-mode of surface plasmon polaritons (SPPs) can be excited at the interface of a metal layer and a dielectric medium. The E-mode of the SPPs is excited due to reflection of the TM-mode from the boundary of inhomogeneity in the metal layer. The interference of these modes leads to the formation of the SPP vortices in the points of minima of the mode field in some components of the Poynting vector of the SPP. The SPP interference vortex pattern changes depending on the curvature of the boundary of inhomogeneity in the metal layer, and the vortices appear and disappear in the components of the Poynting vector.

Nanoscale on-chip all-optical logic parity checker in integrated plasmonic circuits in optical communication range.

The nanoscale chip-integrated all-optical logic parity checker is an essential core component for optical computing systems and ultrahigh-speed ultrawide-band information processing chips. Unfortunately, little experimental progress has been made in development of these devices to date because of material bottleneck limitations and a lack of effective realization mechanisms. Here, we report a simple and efficient strategy for direct realization of nanoscale chip-integrated all-optical logic parity checkers in integrated plasmonic circuits in the optical communication range. The proposed parity checker consists of two-level cascaded exclusive-OR (XOR) logic gates that are realized based on the linear interference of surface plasmon polaritons propagating in the plasmonic waveguides. The parity of the number of logic 1s in the incident four-bit logic signals is determined, and the output signal is given the logic state 0 for even parity (and 1 for odd parity). Compared with previous reports, the overall device feature size is reduced by more than two orders of magnitude, while ultralow energy consumption is maintained. This work raises the possibility of realization of large-scale integrated information processing chips based on integrated plasmonic circuits, and also provides a way to overcome the intrinsic limitations of serious surface plasmon polariton losses for on-chip integration applications.

導体ピラーアレイを用いた表面プラズモンポラリトン干渉による近接場ふく射輸送のスペクトル制御

Spectral control of near-field radiation transfer by interference of Surface Plasmon Polaritons (SPPs) in pillar array structured surface made of nickel was investigated using a numerical simulation based on Maxwell’s electromagnetic wave theory. The electromagnetic field between two pillar array structured surfaces fixed in face to face with a vacuum gap of several hundred nanometers was obtained using a three dimensional Finite Difference Time Domain (FDTD) method and fluctuational electrodynamics (FED). The near-field radiation flux from a high temperature to a low temperature pillar array structured surfaces was evaluated through the summation of normal components of Poynting vector in any direction at the intermediate of the vacuum gap. Through the numerical simulation, it was clarified that the local maximum and the local minimum of near-field radiation flux were shown periodically with increasing height of pillar under the condition of a fixed vacuum gap, which was regarded as interference between the pillar height and an electromagnetic wave propagating in the channel between pillars. Moreover, the dispersion relation of the electromagnetic wave with interference in the channel between pillars is quite similar to the SPPs established in two semi-infinite smooth plates with a nanometer vacuum gap. As a result, it was concluded that the spectral control of near-field radiation transfer was achieved by interference of SPPs in the channel between pillars by tuning the height of pillar.

Narrow-band plasmonic directional excitation of two metallic slits with a coupled cavity.

We investigate theoretically and numerically a model that can achieve narrow-band plasmonic directional excitation in the near-infrared region. The structure is a silver film modified by two uniform metallic slits with a coupled cavity. Our design method is based on the coupled cavity theory, and surface plasmon polaritons (SPPs) interference. The work wavelength region is chosen when the coupled cavity is in resonance. The distance between the two slits is chosen based on SPPs interference. The directional excitation bandwidth can be only 37.9 nm. The finite-difference time-domain method is carried to verify our design method.

Surface Plasmon Polariton-coupled Waveguide Back Reflector in Thin-film Silicon Solar Cell

Surface plasmon polariton (SPP) waveguide-coupled back reflector geometry is proposed for efficient light trapping and broadband absorption enhancement in thin-film silicon solar cells. The proposed geometry takes advantage of the localized surface plasmon (LSP) enhancement, Fabry-Perot (FP) resonance, and strong electric field confinement resulting from the SPP interference in a metal waveguide. It is shown that the designed light trapping structures contribute to significant light trapping and enhancement in the red to near-infrared part of the solar spectrum. For a thin-film silicon solar cell of 220-nm thickness, an absorption enhancement of 153 % is obtained when compared to a bare silicon solar cell. In comparison to other SPP-excited back reflection geometries, such as nano-gratings and nano-grooves, the proposed configuration shows a higher absorption enhancement factor and uniform field distribution inside the silicon layer. These results are expected to introduce new directions in the design of optimized nanoscale back reflectors in thin-film silicon solar cells.

Period reduction lithography in normal UV range with surface plasmon polaritons interference and hyperbolic metamaterial multilayer structure

A plasmonic lithography method is proposed to generate a large-area, period-reduced, subwavelength one-dimensional grating pattern. It is demonstrated with a surface plasmon polaritons interference effect and a hyperbolic metamaterial multilayer structure by UV radiation at 405 nm wavelength. Photoresist patterns of 1.5 × 1.5 cm2 area with 350 nm period and 100 nm linewidth were fabricated on polyethylene terephthalate films by using a 700-nm-period Al grating mask and exposed to a transverse magnetic polarized laser. The proposed lithography approach provides a cost-effective and less laborious pathway for the fabrication of large-area periodic nano-patterns.

Dichroic directional excitation of surface plasmon based on an integer-programming model.

A silver film perforated with two subwavelength uniform slits is proposed for dichroic directional excitation of surface plasmon polaritons (SPPs). Under backside oblique illumination, the SPPs for two work wavelengths can propagate along the two opposite directions or in the same direction. Based on SPP interference, an integer-programming model is established for dichroic directional excitation of SPPs. The branch and bound method is introduced to find the optimal solutions for the integer-programming model, and therefore, the parameters of the structure and illumination angles can be obtained. The field distribution of the structure is investigated by using the finite-difference time-domain method (FDTD) to verify our design. Our theoretical model can achieve dichroic directional excitation of SPPs, simultaneously.

Structured metal thin film as an asymmetric color filter: the forward and reverse plasmonic halos.

We observe asymmetric color filtering under unpolarized incidence in a structured metallic (Ag) film, where the center of an optically thick circular Ag disk surrounded by a step gap appears dark when observed from one side, and bright from the other. The latter situation corresponds to abnormally high optical transmission through the optically thick film. We explain this by a three-step process: coupling of photons to surface plasmon polaritons (SPPs), wave interference of SPPs forming resonant cavity modes, and out-coupling from SPPs to photons. Full wave electromagnetic simulations based on the finite element method support our findings. These results may have potential applications in areas such as optical color filtering and biosensing via dielectric detection within the step gap plasmonic cavity.

Direct observation of bosonic quantum interference of surface plasmon polaritons using photon-number-resolving detectors

Quantum plasmonics is a field of research combining plasmonics with quantum optics and investigates interactions between photons and metallic nanostructures. So far, it has been proven that quantum properties of single photons to excite single surface plasmon polaritons (SPPs) are preserved in the process of photon-SPP-photon mode conversion in plasmonic nanostructures, which suggests the potential application of SPPs to the quantum information processing (QIP). Recently the Hong-Ou-Mandel (HOM) interference of single SPPs was observed in a plasmonic circuitry. However, the visibility was below the classical limit (50%) due to the simultaneous excitation of distinguishable SPP modes. We employed a directional coupler based on long-range surface-plasmon-polariton waveguides (LRSPP-DC) and superconducting photon-number-resolving detectors to directly observe the bosonic quantum interference of single SPPs beyond the classical limit. In addition, we demonstrated the indistinguishability of photons that excite single SPPs is well preserved in the process of photon-SPP mode conversion.