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We investigated hybrid functional transparent conductive electrodes (HFTCEs) composed of indium-tin-oxide (ITO) and silver nanowires (AgNWs) for the enhancement of output efficiency in GaN-based ultraviolet light-emitting diodes (UVLEDs). The HFTCEs demonstrated an optical transmittance of 69.5% at a wavelength of 380 nm and a sheet resistance of 16.4 Ω/sq, while the reference ITO TCE exhibited a transmittance of 76.4% and a sheet resistance of 18.7 Ω/sq. Despite the 8.9% lower optical transmittance, the UVLEDs fabricated with HFTCEs achieved a 25% increase in output efficiency compared to reference UVLEDs. This improvement is attributed to the HFTCE's twofold longer current spreading length under operating forward voltages, and more significantly, the enhanced out-coupling of localized surface plasmon (LSP) resonance with the trapped wave-guided light modes. [ABSTRACT FROM AUTHOR]

As the driving source, highly efficient silicon-based light emission is urgently needed for the realization of optoelectronic integrated chips. Here, we report that enhanced green electroluminescence (EL) can be obtained from oxygen-doped silicon nitride (SiNx:O) films based on an ordered and tunable Ag nanocavity array with a high density by nanosphere lithography and laser irradiation. Compared with that of a pure SiNxO device, the green electroluminescence (EL) from the SiNx:O/Ag nanocavity array device can be increased by 7.1-fold. Moreover, the external quantum efficiency of the green electroluminescence (EL) is enhanced 3-fold for SiNx:O/Ag nanocavity arrays with diameters of 300 nm. The analysis of absorption spectra and the FDTD calculation reveal that the localized surface plasmon (LSP) resonance of size-controllable Ag nanocavity arrays and SiNx:O films play a key role in the strong green EL. Our discovery demonstrates that SiNx:O films coupled with tunable Ag nanocavity arrays are promising for silicon-based light-emitting diode devices of the AI period in the future. [ABSTRACT FROM AUTHOR]

Tip-enhanced Raman spectroscopy (TERS) has recently been developed to push the spatial resolution down to single-chemical-bond scale. The morphology of the scanning tip, especially the atomistic protrusion at the tip apex, plays an essential role in obtaining both high spatial resolution and large field enhancement at the Ångström level. Although it is very difficult to directly characterize the atomistic structures of the tip, the Raman scattering from the apex’s own vibrations of the metal tip can provide valuable information about the stacking of atoms at the tip apex. However, conventional quantum chemistry packages can only simulate the Raman scattering of small metal clusters with few atoms due to huge computational cost, which is not enough since the shaft of the tip behind the apex also makes significant contributions to the polarizabilities of the whole tip. Here we propose an atomistic polarization model to simulate the Raman spectra of large metal tips at subwavelength scales based on the combination of the atomistic discrete dipole approximation model and the density functional theory. The atomistic tip with different sizes and stacking structures is considered in its entirety during the calculation of polarizabilities, and only the vibrational contributions from the tip apex are taken into account to simulate the Raman spectra of the tip. The Raman spectral features are found to be very sensitive to the local constituent element at the tip apex, atomic stacking modes, and shape of the tip apex, which can thus be used as a fingerprint to identify different atomistic structures of the tip apex. Moreover, our approaches can be extended to the metal tips with sub-wavelength sizes, making it possible to consider both the large scale and the atomistic detail of the tip simultaneously. The method presented here can be used as a basic tool to simulate the Raman scattering process of the metal tips and other nanostructures in an economic way, which is beneficial for understanding the roles of atomistic structures in tip- and surface-enhanced spectroscopies.

As the driving source, highly efficient silicon-based light emission is urgently needed for the realization of optoelectronic integrated chips. Here, we report that enhanced green electroluminescence (EL) can be obtained from oxygen-doped silicon nitride (SiNx:O) films based on an ordered and tunable Ag nanocavity array with a high density by nanosphere lithography and laser irradiation. Compared with that of a pure SiNxO device, the green electroluminescence (EL) from the SiNx:O/Ag nanocavity array device can be increased by 7.1-fold. Moreover, the external quantum efficiency of the green electroluminescence (EL) is enhanced 3-fold for SiNx:O/Ag nanocavity arrays with diameters of 300 nm. The analysis of absorption spectra and the FDTD calculation reveal that the localized surface plasmon (LSP) resonance of size-controllable Ag nanocavity arrays and SiNx:O films play a key role in the strong green EL. Our discovery demonstrates that SiNx:O films coupled with tunable Ag nanocavity arrays are promising for silicon-based light-emitting diode devices of the AI period in the future.

Electron energy loss spectroscopy (EELS) is often utilized to characterize localized surface plasmon modes supported by plasmonic antennas. However, the spectral resolution of this technique is only mediocre, and it can be rather difficult to resolve modes close in the energy, such as coupled modes of dimer antennas. Here, we address this issue for a case study of the dimer plasmonic antenna composed of two gold discs. We analyze four nearly degenerate coupled plasmon modes of the dimer: longitudinal and transverse bonding and antibonding dipole modes. With a traditional approach, which takes into account the spectral response of the antennas recorded at specific points, the modes cannot be experimentally identified with EELS. Therefore, we employ the spectral and spatial sensitivity of EELS simultaneously. We propose several metrics that can be utilized to resolve the modes. First, we utilize electrodynamic simulations to verify that the metrics indeed represent the spectral positions of the plasmon modes. Next, we apply the metrics to experimental data, demonstrating their ability to resolve three of the above-mentioned modes (with transverse bonding and antibonding modes still unresolved), identify them unequivocally, and determine their energies. In this respect, the spatio-spectral metrics increase the information extracted from electron energy loss spectroscopy applied to plasmonic antennas.

Circular dichroism (CD) effects have broad applications in fields including biophysical analysis, analytical chemistry, nanoscale imaging, and nanosensor design. Herein, a novel design of a tilted F-type chiral metal nanostructure composed of circular nanoholes with varying radii has been proposed to achieve remarkable CD effects, and the results demonstrate the generation of a significant current oscillation at the sharp edges where the nanoholes overlap under circularly polarized light, resulting in a strong CD effect. The CD effect can reach up to 7.5%. Furthermore, spectral modulation of the resonant wavelength can be achieved by adjusting the structural parameters, which enhances the tunability of the structure. Overall, these results provide theoretical or practical guidance for enhancing the circular dichroism signal strength of chiral metal nanostructures and designing new types of two-dimensional chiral structures. [ABSTRACT FROM AUTHOR]

Localized surface plasmon polaritons can confine the optical field to a single-nanometer-scale area, strongly enhancing the interaction between photons and molecules. Theoretically, the ultimate enhancement might be achieved by reducing the “photon size” to the molecular extinction cross-section. In addition, desired control of electronic transitions in molecules can be realized if the “photon shape” can be manipulated on a single-nanometer scale. By matching the photon shape with that of the molecular electron wavefunction, optically forbidden transitions can be induced efficiently and selectively, enabling various unconventional photoreactions. Here, we demonstrate the possibility of forming single-nanometer-scale, highly intense fields of optical vortices using designed plasmonic nanostructures. The orbital and spin angular momenta provided by a Laguerre–Gaussian beam are selectively transferred to the localized plasmons of a metal multimer structure and then confined into a nanogap. This plasmonic nano-vortex field is expected to fit the molecular electron orbital shape and spin with the corresponding angular momenta.

Surface Plasmonic Resonance (SPR) induced by metallic nanoparticles can be exploited to enhance the response of photodetectors (PD) to a large degree. Since the interface between metallic nanoparticles and semiconductors plays an important role in SPR, the magnitude of the enhancement is highly dependent on the morphology and roughness of the surface where the nanoparticles are distributed. In this work, we used mechanical polishing to produce different surface roughnesses for the ZnO film. Then, we exploited sputtering to fabricate Al nanoparticles on the ZnO film. The size and spacing of the Al nanoparticles were adjusted by sputtering power and time. Finally, we made a comparison among the PD with surface processing only, the Al-nanoparticles-enhanced PD, and the Al-nanoparticles-enhanced PD with surface processing. The results showed that increasing the surface roughness could enhance the photo response due to the augmentation of light scattering. More interestingly, the SPR induced by the Al nanoparticles could be strengthened by increasing the roughness. The responsivity could be enlarged by three orders of magnitude after we introduced surface roughness to boost the SPR. This work revealed the mechanism behind how surface roughness influences SPR enhancement. This provides new means for improving the photo responses of SPR-enhanced photodetectors. [ABSTRACT FROM AUTHOR]

Surface-Enhanced Raman Spectroscopy is a powerful technique that boosts the distinctive fingerprint signals of molecules, making them more accessible for analysis. It utilizes metallic nanoparticles, acting as amplifiers, to greatly enhance the signals emitted by the molecules. This study aimed to explore the SERS potential of gold nanoparticles (AuNPs) with different geometries using a non-resonant molecule, 4-MBA. Nanospheres (14±2 nm), nanorods (11±2 nm x 50±7 nm) and nanostars (38±4 nm) were synthesized via the HAuCl4 reduction method. All three AuNP geometries exhibited a remarkable enhancement of the Raman signal of 4-MBA by a magnitude of 104. Notably, only gold nanorods and nanostars displayed localized surface plasmon within the biological window, making them highly suitable for biological sample analysis. Meanwhile, the application of gold nanospheres should be limited to chemical SERS detection. These findings confirm the potential use of these nanostructures as SERS substrates for studying molecules with low molar...

Using finite element calculations, we investigated the near field properties of two types of commonly used metal nanostructures (a tip-substrate model representing a scanning tunneling microscope type setup (TS) and a nanoparticle-on-mirror (NPoM) configuration) with atomic sharpness and extreme focusing capabilities. The spatial confinement and electric field enhancement of the local field as well as the fluorescence quantum efficiency of a model molecule (as represented by an oscillating dipole) in the cavity region of the two models were systematically studied. It was found that the TS model tends to support higher local electric field enhancement while the NPoM model can provide a more localized plasmon electric field near the nanoparticle. Calculations with the radiating model molecule indicate that both TS and NPoM can cause significant enhancements to the non-radiative decay rates at the order of 106 in the wavelength range of 500–1000 nm. The TS model shows better performance for the radiative enhancements and the resulting emission quantum yield. These results are not only helpful to improve the understanding of such important nanocavities but also supply a reference for their further applications in different areas.

We report on a self-referenced refractive index optical sensor based on Au nanoislands. The device consists of a random distribution of Au nanoislands formed by dewetting on a planar SiO2/metal Fabry–Pérot cavity. Experimental and theoretical studies of the reflectance of this configuration reveal that its spectral response results from a combination of two resonances: a localized surface plasmon resonance (LSPR) associated to the Au nanoislands and the lowest-order anti-symmetric resonance of the Fabry–Pérot cavity. When the device is immersed in different fluids, the LSPR contribution provides high sensitivity to refractive index variations of the fluid, whereas those refractive index changes have little impact on the Fabry–Pérot resonance wavelength, allowing its use as a reference signal. The self-referenced sensor exhibits a spectral sensitivity of 212 nm/RIU (RIU: refractive index unit), which is larger than those of similar structures, and an intensity sensitivity of 4.9 RIU−1. The proposed chip-based architecture and the low cost and simplicity of the Au nanoisland synthesis procedure make the demonstrated sensor a promising self-referenced plasmonic sensor for compact biosensing optical platforms based on reflection mode operation. [ABSTRACT FROM AUTHOR]

Circular dichroism (CD) effects have broad applications in fields including biophysical analysis, analytical chemistry, nanoscale imaging, and nanosensor design. Herein, a novel design of a tilted F-type chiral metal nanostructure composed of circular nanoholes with varying radii has been proposed to achieve remarkable CD effects, and the results demonstrate the generation of a significant current oscillation at the sharp edges where the nanoholes overlap under circularly polarized light, resulting in a strong CD effect. The CD effect can reach up to 7.5%. Furthermore, spectral modulation of the resonant wavelength can be achieved by adjusting the structural parameters, which enhances the tunability of the structure. Overall, these results provide theoretical or practical guidance for enhancing the circular dichroism signal strength of chiral metal nanostructures and designing new types of two-dimensional chiral structures.

The sun provides a plentiful and inexpensive source of carbon-neutral energy that has yet to be fully utilized. This is a major driving force behind the development of organic photovoltaic (OPV) materials and devices, which are expected to offer benefits such as low cost, flexibility, and widespread availability. For the photovoltaic performance enhancement of the inverted ZnO-nanorods (NR)/organic hybrid solar cells with poly(3-exylthiophene):(6,6)-phenyl-C61-butyric-acid-methylester (P3HT:PCBM) and poly (3,4-ethylenedioxythiophene):poly (styrenesulfonate) (PEDOT:PSS) active layers, gold nanoparticles (Au-NPs) were introduced into the interface between indium-thin-oxide cathode layer and ZnO cathode buffer layer, and the efficiency improvement was observed. It's worth noting that adding Au NPs had both a positive and negative impact on device performance. Au NPs were shown to be advantageous to localized surface plasmon resonance (LSPs) in the coupling of dispersed light from ZnO NRs in order to extend the light's path length in the absorbing medium. Although the light absorption in the active layer could be enhanced, Au NPs might also act as recombination centers within the active layer. To avoid this adverse effect, Au NPs are covered by the ZnO seeded layer to prevent Au NPs from direct contact with the active layer. The dominant surface plasmonic effect of Au NPs increased the photoelectric conversion efficiency from 2.4% to 3.8%.

Abstract Owing to the intense carrier recombination and limited optical absorption, the as‐fabricated CsPbBr3 visible light photodetectors (PDs) are far from practical application. In this work, we have demonstrated performance‐improved metal‐semiconductor‐metal (MSM) structured CsPbBr3 visible light PDs realized by the decoration of sputtered Au nanoparticles (NPs). It showed that the Au NPs on the CsPbBr3 exhibited synergistic benefits including improving the photogenerated charge carriers’ lifetime and enhancing the optical absorption of the CsPbBr3, both of which are fundamental factors for the performance‐improved PDs. Electrical characterizations showed that localized Schottky junctions formed at the Au NPs/CsPbBr3 interface. In addition, optical investigations showed that effective resonant coupling occurred between the localized surface plasmon resonance effects of Au NPs and excitons in the CsPbBr3. As a result, the on‐off switching of the Au‐decorated CsPbBr3 photodetector increased by 13 times compared with that of the pristine one. Meanwhile, the peak photo sensitivity of the CsPbBr3 photodetector was increased from 0.088 to 0.61 A W‐1 after the decoration of Au NPs. It is believed that the results shown in this work will provide pathways for fabricating high‐performance CsPbBr3 PDs and other similar devices in the future.

Plasmonic phenomena on the surface between metal and dielectric have received extensive attention, and have boosted a series of exciting techniques. Plasmonics describes the interaction between light and electronics and shows great potential in nanophotonics, optoelectronic devices, quantum physics, and surface-enhanced spectroscopy, etc. However, plasmonic phenomena are always suffering from the inherent loss issue of plasmonic materials at optical frequency, which has restricted further applications of plasmonics. In this review, we focus on the technique of waveguide effective plasmonics, which is a feasible low-loss realization of plasmonic metamaterials in lower frequency based on the structural dispersion. This review provides the underlying physics of the waveguide effective plasmonics and its applications varying from classical plasmonic concepts to novel effective plasmonic devices. Finally, we make a brief discussion on the direction of future researches and a prospect of the potential applications.

Surface Plasmonic Resonance (SPR) induced by metallic nanoparticles can be exploited to enhance the response of photodetectors (PD) to a large degree. Since the interface between metallic nanoparticles and semiconductors plays an important role in SPR, the magnitude of the enhancement is highly dependent on the morphology and roughness of the surface where the nanoparticles are distributed. In this work, we used mechanical polishing to produce different surface roughnesses for the ZnO film. Then, we exploited sputtering to fabricate Al nanoparticles on the ZnO film. The size and spacing of the Al nanoparticles were adjusted by sputtering power and time. Finally, we made a comparison among the PD with surface processing only, the Al-nanoparticles-enhanced PD, and the Al-nanoparticles-enhanced PD with surface processing. The results showed that increasing the surface roughness could enhance the photo response due to the augmentation of light scattering. More interestingly, the SPR induced by the Al nanoparticles could be strengthened by increasing the roughness. The responsivity could be enlarged by three orders of magnitude after we introduced surface roughness to boost the SPR. This work revealed the mechanism behind how surface roughness influences SPR enhancement. This provides new means for improving the photo responses of SPR-enhanced photodetectors.

Metal-oxides hold promise as superior plasmonic materials in the mid-infrared compared to metals, although their integration over established material technologies still remains challenging. We demonstrate localized surface plasmons in self-assembled, hemispherical CdZnO metal-oxide nanoparticles on GaAs, as a route to enhance the absorption in mid-infrared photodetectors. In this system, two localized surface plasmon modes are identified at 5.3 and 2.7 μm, which yield an enhancement of the light intensity in the underlying GaAs. In the case of the long-wavelength mode the enhancement is as large as 100 near the interface, and persists at depths down to 50 nm. We show numerically that both modes can be coupled to infrared intersubband transitions in GaAs-based multiple quantum wells, yielding an absorbed power gain as high as 5.5, and allowing light absorption at normal incidence. Experimentally, we demonstrate this coupling in a nanoparticle/multiple quantum well structure, where under p-polarization the intersubband absorption is enhanced by a factor of 2.5 and is still observed under s-polarization, forbidden by the usual absorption selection rules. Thus, the integration of CdZnO on GaAs can help improve the figures of merit of quantum well infrared photodetectors, concept that can be extended to other midinfrared detector technologies.

The electromagnetic multipole method has been extensively adopted for a better understanding of the physical mechanism of localized surface plasmon. In this work, we quantitatively decomposed the total extinction spectra of typical silver nanoparticles into multipole components, which are shown to be quite different from qualitative assignment of resonance peaks reported previously. Taking the quasi-normal mode method as reference standard, we examined the scope of application of the electromagnetic multipole method in assigning plasmonic resonance peaks, and pointed out the necessity of employing eigenmode-based approaches when interpreting plasmonic spectra, which can hopefully lead to more physical insights into the underlying mechanisms of plasmonics phenomena.

Infrared detection technology has been widely applied in many areas. Unlike internal photoemission and the photoelectric mechanism, which are limited by the interface barrier height and material bandgap, the research of the hot carrier effect from nanometer thickness of metal could surpass the capability of silicon-based Schottky devices to detect mid-infrared and even far-infrared. In this work, we investigate the effects of physical characteristics of Cr nanometal surfaces and metal/silicon interfaces on hot carrier optical detection. Based on the results of scanning electron microscopy, atomic force microscopy, and X-ray diffraction analysis, the hot carrier effect and the variation of optical response intensity are found to depend highly on the physical properties of metal surfaces, such as surface coverage, metal thickness, and internal stress. Since the contact layer formed by Cr and Si is the main role of infrared light detection in the experiment, the higher the metal coverage, the higher the optical response. Additionally, a thicker metal surface makes the hot carriers take a longer time to convert into current signals after generation, leading to signal degradation due to the short lifetime of the hot carriers. Furthermore, the film with the best hot carrier effect induced in the Cr/Si structure is able to detect an infrared signal up to 4.2 μm. Additionally, it has a 229 times improvement in the signal-to-noise ratio (SNR) for a single band compared with ones with less favorable conditions. [ABSTRACT FROM AUTHOR]

Therefore, it is reasonable to define the effective permittivity in the TE SB 10 sb mode of rectangle waveguide as I i SB eff sb = I i SB I r i sb - ( I i /2 I w i ) SP 2 sp , such that the effective permittivity I i SB eff sb reflects the effective property of TE SB 10 sb mode in the rectangle waveguide. The waveguide effective plasmonics is realized by utilizing the structural dispersion of waveguide, and the effective negative permittivity can be obtained with non-dispersive and low-loss dielectrics with positive permittivity [[70]]. Keywords: localized surface plasmon; plasmonics; structural dispersion; surface plasmon polaritons; waveguide effective plasmonics EN localized surface plasmon plasmonics structural dispersion surface plasmon polaritons waveguide effective plasmonics 1659 1676 18 05/12/22 20220401 NES 220401 1 Introduction Since Mie and Ritchie first systematically described the fundamental physics on the interfaces between conductors and insulators for small particles and flat films, respectively [[1]], various researches on the surface electron oscillations have been widely conducted, including the propagating electromagnetic wave coupled to the conductor and dielectric interfaces, and the non-propagating resonance in the subwavelength nanostructure coupled to electromagnetic fields. In the work [[95]], waveguide effective SPP propagation is induced through two stacked half-mode SIWs (effective relative permittivities of filled dielectrics have opposite signs), achieving a sharp zero-transmission spectrum in waveguide response. The effective permittivity is corresponding to the propagating constant in the waveguide, and specifically, the effective permittivity is positive or negative when the waveguide is operating in propagating or below cut-off mode, respectively, and the effective permittivity equals zero when the waveguide is exactly at the cut-off frequency. [Extracted from the article]

Using the finite-difference time-domain (FDTD) method, we designed an ultra-thin Ge/GaAs/P3HT:PCBM hybrid solar cell (HSC), which showed good effects of ultra-wideband (300 nm–1200 nm), high absorption, and a short-circuit current density of 44.7 mA/cm2. By changing the thickness of the active layer P3HT:PCBM, we analyzed the capture of electron-hole pairs. We also studied the effect of Al2O3 on the absorption performance of the cell. Through adding metal Al nanoparticles (Al-NPs) and then analyzing the figures of absorption and electric field intensity, we found that surface plasma is the main cause of solar cell absorption enhancement, and we explain the mechanism. The results show that the broadband absorption of the solar cell is high, and it plays a great role in capturing sunlight, which will be of great significance in the field of solar cell research. [ABSTRACT FROM AUTHOR]

Localized plasmon resonance of a metal nanoantenna is determined by its size, shape and environment. Here, we diminish the size dependence by using multilayer metamaterials as epsilon-near-zero (ENZ) substrates. By means of the vanishing index of the substrate, we show that the spectral position of the plasmonic resonance becomes less sensitive to the characteristics of the plasmonic nanostructure and is controlled mostly by the substrate, and hence, it is pinned at a fixed narrow spectral range near the ENZ wavelength. Moreover, this plasmon wavelength can be adjusted by tuning the ENZ region of the substrate, for the same size nanodisk (ND) array. We also show that the difference in the phase of the scattered field by different size NDs at a certain distance is reduced when the substrate is changed to ENZ metamaterial. This provides effective control of the phase contribution of each nanostructure. Our results could be utilized to manipulate the resonance for advanced metasurfaces and plasmonic applications, especially when precise control of the plasmon resonance is required in flat optics designs. In addition, the pinning wavelength can be tuned optically, electrically and thermally by introducing active layers inside the hyperbolic metamaterial.

Abstract Absorption enhancement based on interaction between the localized surface plasmon (LSP) and molecular exciton is one of the most important phenomena for the development of high-performance solar devices. In this study, hybrids of plasmonic metal nanoparticles and dye molecules have been developed, which exhibit enhanced absorption at precisely tuned wavelengths in a visible region. The hybrids consist of a porphyrin derivative, which has four absorption peaks (Q-bands) in a range of 500–700 nm, and triangular silver nanoprisms (AgPRs), which are developed by us to exhibit precisely tuned LSP resonance wavelengths. Absorption enhancement over the whole Q-band range is induced by the combined use of three kinds of AgPRs of different aspect ratios. Furthermore, the quantitative evaluation of absorption enhancement based on the LSP-based fluorescence enhancement phenomenon has demonstrated that efficient absorption enhancement can be effected at multiple wavelengths.

We report on a self-referenced refractive index optical sensor based on Au nanoislands. The device consists of a random distribution of Au nanoislands formed by dewetting on a planar SiO2/metal Fabry–Pérot cavity. Experimental and theoretical studies of the reflectance of this configuration reveal that its spectral response results from a combination of two resonances: a localized surface plasmon resonance (LSPR) associated to the Au nanoislands and the lowest-order anti-symmetric resonance of the Fabry–Pérot cavity. When the device is immersed in different fluids, the LSPR contribution provides high sensitivity to refractive index variations of the fluid, whereas those refractive index changes have little impact on the Fabry–Pérot resonance wavelength, allowing its use as a reference signal. The self-referenced sensor exhibits a spectral sensitivity of 212 nm/RIU (RIU: refractive index unit), which is larger than those of similar structures, and an intensity sensitivity of 4.9 RIU−1. The proposed chip-based architecture and the low cost and simplicity of the Au nanoisland synthesis procedure make the demonstrated sensor a promising self-referenced plasmonic sensor for compact biosensing optical platforms based on reflection mode operation.

Metallic nanowires have been utilized as a platform for propagating surface plasmon (SPs) fields. To be exploited for applications such as plasmonic circuits, manipulation of localized field propagating pattern is also important. In this study, we calculated the field distributions of localized surface plasmons (LSPs) on the specifically shaped nanostructures and explored the feasibility of manipulating LSP fields. Specifically, plasmonic fields were calculated at different wavelengths for a nanoscale rod array (I-shaped), an array connected with two nanoscale rods at right angles (T-shaped), and an array with three nanoscale rods at 120° to each other (Y-shaped). Three different types of nanostructures are suggested to manipulate the positions of LSP fields collaborating with adjustment of wavelength, polarization, and incident orientation of light source. The results of this study are important not only for the understanding of the wavelength-dependent surface plasmon field localization mechanism but also for the applicability of swept source-based plasmonic techniques or designing a plasmonic circuit. [ABSTRACT FROM AUTHOR]

A promising route to realize solar-to-chemical energy conversion resorts to water splitting using plasmon photocatalysis. However, the ultrafast carrier dynamics and underlying mechanism in such processes has seldom been investigated, especially when the single-atom catalyst is introduced. Here, from the perspective of quantum dynamics at the atomic length scale and femtosecond time scale, we probe the carrier and structural dynamics of plasmon-assisted water splitting on an Ag-alloyed Pt single-atom catalyst, represented by the Ag19Pt nanocluster. The substitution of an Ag atom by the Pt atom at the tip of the tetrahedron Ag20 enhances the interaction between water and the nanoparticle. The excitation of localized surface plasmons in the Ag19Pt cluster strengthens the charge separation and electron transfer upon illumination. These facts cooperatively turn on more than one charge transfer channels and give rise to enhanced charge transfer from the metal nanoparticle to the water molecule, resulting in rapid plasmon-induced water splitting. These results provide atomistic insights and guidelines for the design of efficient single-atom photocatalysts for plasmon-assisted water splitting.

Traditional methods of polymers joining for industrial applications are limited to lasers, induction, or conduction heating. It is difficult to achieve precision and efficiency in large-scale applications simultaneously. In this paper, we report a precise microwave welding method induced by localized surface plasmons of metallic macro-gaps under microwave excitation. The proposed method uses energy from well-developed commercial microwaves and benefits from the precision of localized surface plasmons, an oscillating electron cloud excited by electromagnetic waves, which is currently under investigation only at the micro or nanoscales. This method is employed in plastic microwave welding, and the numerical analyses and experimental results reveal that, in comparison to traditional microwave heating methods, this process effectively focuses microwave energy to achieve precision area heating of a diameter of 4 mm or less; this results in a temperature increase at a rate of 333.8 °C/s, and the maximum tensile strength of the welded samples reaches as high as 668 N, which is comparable to that of the base material. The results demonstrate that the processing method is an environmentally friendly approach characterized by high quality, efficiency, and low energy consumption. [Display omitted] • Develop a novel plasmon local field enhancement assisted microwave welding method. • Achieve focused microwave energy and precise polymer heating. • Welded samples exhibit excellent mechanical properties. • Method offers high quality, efficiency, cleanliness, and low consumption advantages. [ABSTRACT FROM AUTHOR]

We report a novel type of electromagnetically induced transparency (EIT) analogue based on metamaterials (MMs) with hybrid structures, in which spiral and cut-wire structures serve as bright-mode resonators with the spoof electric localized surface plasmons and electric dipole resonance. With the simulations and experiments, the EIT analogue generated by the frequency detuning and hybridization between the resonators is verified. The simulated surface charge density and electric and magnetic field distributions, together with the theoretical analysis based on the Lorentz oscillator model, reveal the principle of the EIT analogue. Moreover, the transmission window of the MM demonstrates linear dependence on the refractive index’s change of surrounding media, showing the potential as a tool for environmental detection. [ABSTRACT FROM AUTHOR]

Using the finite-difference time-domain (FDTD) method, we designed an ultra-thin Ge/GaAs/P3HT:PCBM hybrid solar cell (HSC), which showed good effects of ultra-wideband (300 nm–1200 nm), high absorption, and a short-circuit current density of 44.7 mA/cm2. By changing the thickness of the active layer P3HT:PCBM, we analyzed the capture of electron-hole pairs. We also studied the effect of Al2O3 on the absorption performance of the cell. Through adding metal Al nanoparticles (Al-NPs) and then analyzing the figures of absorption and electric field intensity, we found that surface plasma is the main cause of solar cell absorption enhancement, and we explain the mechanism. The results show that the broadband absorption of the solar cell is high, and it plays a great role in capturing sunlight, which will be of great significance in the field of solar cell research.

Abstract In order to enhance the refractive index sensing performance of simple particle arrays, a structure, consisting of Au/SiO2 triangle arrays layers and reflection Au substrate, with increasing size and lengthening tips of triangles, is studied. The triangle arrays are modeled after an experimentally realizable “imprint” of microsphere lithography. Numerical calculation was carried out to study its optical properties and spectral sensitivity. The calculation results show that a large local enhancement of electric field (61 times) and simultaneously high absorption is due to combination of the resonance absorption of Au triangle disks, plasmonic couplings between the Au triangle disks and the Au film, and the high-density packing of triangle disks. The absorption peaks were not detuned when the gap between neighboring tips of the triangles varied from 10 to 50 nm. When the thickness of SiO2 layer increased from 10 to 50 nm, the absorption peak shifted to longer wavelengths and the amplitude rises quickly signaling the dominance of the gap mode resonance between the two Au layers. As the thickness of the top Au layer varies from 10 to 50 nm, the absorption peak is also red shifted and the peak amplitude increases. The full width at half maximum of the peaks for high absorption (> 90%) is about 5 nm. When fixing the gap, the thicknesses of Au/SiO2 triangle layer, and increasing the surrounding refractive index from 1.33 to 1.36, the absorption peaks shifted quickly, with a refractive index sensitivity and figure of merit as high as 660 nm per refractive index unit and 132, respectively. Such arrays can be easily fabricated by using microsphere array as projection masks and find application in refractive index monitoring of liquid and identification of gas and liquid phases.

Abstract Three kinds of typical structures, hemi-/spherical nanoparticles/nanoparticle dimers on the substrate and spherical nanoparticles/nanoparticle dimers half-buried into the substrate, are used for FDTD simulation to theoretically discuss the influence of the substrate to the localized surface plasmon (LSP) coupling when the metal nanoparticles/nanoparticle dimers are locating near a substrate. Simulated results show that the dependencies between the LSP coupling wavelength and the refractive index of the substrate for different structures are not the same, which can be attributed to the different polarization field distributions of LSPs. When light is incident from different directions, the LSP coupling strength are not the same as well and the ratios of the scattering peak intensities depend on the position of the metal nanoparticles or nanoparticle dimers. These phenomenon can be explained by the difference of the local driving electric field intensities which is modulated by the interface between the air and the substrate.

In this paper, we present a periodic nanostructure based on two types of silver plasmonic nanoantennas in order to enhance light absorption in graphene with a wavelength between 300 nm and 1800 nm. In this structure, a single graphene layer is located between two hexagonal boron nitride (hBN) layers, where this set is sandwiched between two layers of SiO2. The first nanoantenna type is a trapezoid inside SiO2, adjacent to the lower hBN, which focuses light within the graphene layer by intensifying the localized surface plasmons, triggering a significant increase in the absorption of the solar spectrum by graphene. The extent of this increase changes with varying bases of the trapezoid. The second nanoantenna type is in the same structure and contains two unequal trapezoids adjacent to each other. By adjusting the bases of these trapezoids, a relatively uniform broadband absorption spectrum is achieved which significantly enhances light absorption in the solar spectrum within 300–1800 nm, as compared to the first nanoantenna type. Both the first and second types of nanoantenna provide appropriate absorption at a communication window of 1550 nm as well as at 850 nm and 1300 nm, respectively. [ABSTRACT FROM AUTHOR]

Absorption enhancement based on interaction between the localized surface plasmon (LSP) and molecular exciton is one of the most important phenomena for the development of high-performance solar devices. In this study, hybrids of plasmonic metal nanoparticles and dye molecules have been developed, which exhibit enhanced absorption at precisely tuned wavelengths in a visible region. The hybrids consist of a porphyrin derivative, which has four absorption peaks (Q-bands) in a range of 500–700 nm, and triangular silver nanoprisms (AgPRs), which are developed by us to exhibit precisely tuned LSP resonance wavelengths. Absorption enhancement over the whole Q-band range is induced by the combined use of three kinds of AgPRs of different aspect ratios. Furthermore, the quantitative evaluation of absorption enhancement based on the LSP-based fluorescence enhancement phenomenon has demonstrated that efficient absorption enhancement can be effected at multiple wavelengths. [ABSTRACT FROM AUTHOR]

Localized surface plasmon (LSP) coupling with many radiators are investigated. The LSP is generated by excitation of laser or electron beam on the random Ag nano particles (NPs) and arrayed ones embedded in the p-GaN of green LEDs. They couple with the excitons or radiative recombination in the quantum well (QW) and electron beam, which enhance or suppress the luminescence of the radiators. The photoluminescence (PL) intensity of periodic Ag NPs can get as much as 4.5 times higher than that of bare LED. In addition to the periodic structure, the morphology of Ag NPs also affects the localized SP (LSP) resonance intensity and light scattering efficiency. In the finite difference time domain (FDTD) simulation, five x-polarized dipoles are approximated to five quantum wells. Considering the interaction between the five dipoles and their feedback effect on LSP, the enhancement effect of SP dipole coupling with Ag NPs is amplified and the energy dissipation is reduced. The enhancement of cathodoluminescence (CL) was also found in green LEDs with Ag NPs. The three-body model composed of two orthogonal dipoles and an Ag NP is used for 3D FDTD simulation. The LSP-QWs coupling effect is separated from the electron beam (e-beam)-LSP-QW system by linear approximation. Under the excitation of electron beam, the introduction of z-dipole greatly reduces the energy dissipation. In the cross-sectional sample, z-polarized dipoles in QWs show more coupling strength to the dipole and quadrupole modes of LSP. The perturbation theory is used to separate the LSP coupling effects to x-dipole and z-dipole. At last, the resonator and the antenna effects are discussed for LSP coupling at different positions to the Ag NP.

Metallic nanowires have been utilized as a platform for propagating surface plasmon (SPs) fields. To be exploited for applications such as plasmonic circuits, manipulation of localized field propagating pattern is also important. In this study, we calculated the field distributions of localized surface plasmons (LSPs) on the specifically shaped nanostructures and explored the feasibility of manipulating LSP fields. Specifically, plasmonic fields were calculated at different wavelengths for a nanoscale rod array (I-shaped), an array connected with two nanoscale rods at right angles (T-shaped), and an array with three nanoscale rods at 120° to each other (Y-shaped). Three different types of nanostructures are suggested to manipulate the positions of LSP fields collaborating with adjustment of wavelength, polarization, and incident orientation of light source. The results of this study are important not only for the understanding of the wavelength-dependent surface plasmon field localization mechanism but also for the applicability of swept source-based plasmonic techniques or designing a plasmonic circuit.

We demonstrate the enhancement of fluorescence emitted from dye molecules coupled with two surface plasmons, i.e., silver nanoparticles (AgNPs)-induced localized surface plasmons (LSP) and thin silver (Ag) film supported surface plasmons. Excitation light is illuminated to a SiO2 layer that contains both rhodamine 110 molecules and AgNPs. AgNPs enhances excitation rates of dye molecules in their close proximity due to LSP-induced enhancement of local electromagnetic fields at dye excitation wavelengths. Moreover, the SiO2 layer on one surface of which a 50 nm-thick Ag film is coated for metal cladding (air on the other surface), acts as a waveguide core at the dye emission wavelengths. The Ag film induces the surface plasmons which couple with the waveguide modes, resulting in a waveguide-modulated version of surface plasmon coupled emission (SPCE) for different SiO2 thicknesses in a reverse Kretschmann configuration. We find that varying the SiO2 thickness modulates the fluorescent signal of SPCE, its modulation behavior being in agreement with the theoretical simulation of thickness dependent properties of the coupled plasmon waveguide resonance. This enables optimization engineering of the waveguide structure for enhancement of fluorescent signals. The combination of LSP enhanced dye excitation and the waveguide-modulated version of SPCE may offer chances of enhancing fluorescent signals for a highly sensitive fluorescent assay of biomedical and chemical substances.

Qingwen Zhang,1,2,* Lin Wu,3,* Ten It Wong,4 Jinling Zhang,5 Xiaohu Liu,5 Xiaodong Zhou,4 Ping Bai,3 Bo Liedberg,5 Yi Wang1,2,5 1School of Ophthalmology and Optometry, Eye Hospital, School of Biomedical Engineering, Wenzhou Medical University, 2Wenzhou Institute of Biomaterials and Engineering, Chinese Academy of Sciences, Wenzhou, People’s Republic of China; 3Electronics and Photonics Department, Institute of High Performance Computing, 4Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 5Centre for Biomimetic Sensor Science, School of Materials Science and Engineering, Nanyang Technological University, Singapore *These authors contributed equally to this work Abstract: Localized surface plasmon (LSP) has been widely applied for the enhancement of fluorescence emission for biosensing owing to its potential for strong field enhancement. However, due to its small penetration depth, LSP offers limited fluorescence enhancement over a whole sensor chip and, therefore, insufficient sensitivity for the detection of biomolecules, especially large molecules. We demonstrate the simultaneous excitation of LSP and propagating surface plasmon (PSP) on an Au nanohole array under Kretschmann configuration for the detection of prostate-specific antigen with a sandwich immunoassay. The proposed method combines the advantages of high field enhancement by LSP and large surface area probed by PSP field. The simulated results indicated that a maximum enhancement of electric field intensity up to 1,600 times can be achieved under the simultaneous excitation of LSP and PSP modes. The sandwich assay of PSA carried out on gold nanohole array substrate showed a limit of detection of 140 fM supporting coexcitation of LSP and PSP modes. The limit of detection was approximately sevenfold lower than that when only LSP was resonantly excited on the same substrate. The results of this study demonstrate high fluorescence enhancement through the coexcitation of LSP and PSP modes and pave a way for its implementation as a highly sensitive bioassay. Keywords: gold nanohole array, localized surface plasmon, propagating surface plasmon, fluorescence enhancement, prostate-specific antigen

High spectra response of metal-semiconductor-metal (MSM) ultraviolet photodetectors (UV PDs) based on GaN epitaxial wafers with different diameters of Al nanodots on the surface were realized on free-standing GaN substrates. The UV PDs exhibit low dark current and high spectral response both at room temperature and 150 °C, demonstrating the thermal stability of the fabricated devices. The peak responsivities for the PDs with Al nanodot diameters of 60, 80, and 120 nm are 1.079, 2.420, and 3.096 A/W, showing an enhancement ratio of 32%, 196%, and 280%, respectively, compared to the referential PD without Al nanodots. Numerical investigations reveal that the significant enhancement performance is due to the localized surface plasmon effect, which enhances the localized electric field and produces more electron-hole pairs in the optoelectronic devices, leading to a higher responsivity. The results presented in this paper can promote the development and application for high performance GaN UV PDs.

Motivated by the recent progress in the nanofabrication field and the increasing demand for cost-effective, portable, and easy-to-use point-of-care platforms, localized surface plasmon resonance (LSPR) biosensors have been subjected to a great scientific interest in the last few years. The progress observed in the research of this nanoplasmonic technology is remarkable not only from a nanostructure fabrication point of view but also in the complete development and integration of operative devices and their application. The potential benefits that LSPR biosensors can offer, such as sensor miniaturization, multiplexing opportunities, and enhanced performances, have quickly positioned them as an interesting candidate in the design of lab-on-a-chip (LOC) optical biosensor platforms. This review covers specifically the most significant achievements that occurred in recent years towards the integration of this technology in compact devices, with views of obtaining LOC devices. We also discuss the most relevant examples of the use of the nanoplasmonic biosensors for real bioanalytical and clinical applications from assay development and validation to the identification of the implications, requirements, and challenges to be surpassed to achieve fully operative devices.