Propagating Surface Plasmon Research Articles

Analysis of an Ultra-Wideband, Perfectly Absorptive Fractal Absorber with a Central Square Nanopillar in a Cylindrical Structure with a Square Hollow

In this study, a fractal absorber was designed to enhance light absorptivity and improve the efficiency of converting solar energy into electricity for a range of solar energy technologies. The absorber consisted of multiple layers arranged from bottom to top, and the bottom layer was made of Ti metal, followed by a thin layer of MgF2 atop it. Above the two layers, a structure comprising square pillars formed by three layers of Ti/MgF2/Ti was formed. This pillar was encompassed by a square hollow with cylindrical structures made of Ti material on the exterior. The software utilized for this study was COMSOL Multiphysics® (version 6.0). This study contains an absorption spectrum analysis of the various components of the designed absorber system, confirming the notion that achieving ultra-wideband and perfect absorption resulted from the combination of the various components. A comprehensive analysis was also conducted on the width of the central square pillar, and the analysis results demonstrate the presence of several remarkable optical phenomena within the investigated structure, including propagating surface plasmon resonance, localized surface plasmon resonance, Fabry–Perot cavity resonance, and symmetric coupling plasma modes. The optimal model determined through this software demonstrated that broadband absorption in the range of 276 to 2668 nm, which was in the range of UV-B to near-infrared, exceeded 90.0%. The average absorption rate in the range of 276~2668 nm reached 0.965, with the highest achieving a perfect absorptivity of 99.9%. A comparison between absorption with and without outer cylindrical structures revealed that the resonance effects significantly enhanced absorption efficiency, as evidenced by a comparison of electric field distributions.

Plasmonic Nanostructure Biosensors: A Review.

Plasmonic nanostructure biosensors based on metal are a powerful tool in the biosensing field. Surface plasmon resonance (SPR) can be classified into localized surface plasmon resonance (LSPR) and propagating surface plasmon polariton (PSPP), based on the transmission mode. Initially, the physical principles of LSPR and PSPP are elaborated. In what follows, the recent development of the biosensors related to SPR principle is summarized. For clarity, they are categorized into three groups according to the sensing principle: (i) inherent resonance-based biosensors, which are sensitive to the refractive index changes of the surroundings; (ii) plasmon nanoruler biosensors in which the distances of the nanostructure can be changed by biomolecules at the nanoscale; and (iii) surface-enhanced Raman scattering biosensors in which the nanostructure serves as an amplifier for Raman scattering signals. Moreover, the advanced application of single-molecule detection is discussed in terms of metal nanoparticle and nanopore structures. The review concludes by providing perspectives on the future development of plasmonic nanostructure biosensors.

Electron-exchange and viscosity effects on propagation of surface plasmons in semi-bounded quantum plasmas

Electron-exchange and viscosity effects on propagation of surface plasmons in semi-bounded quantum plasmas

Perfect Solar Absorber Based on Four-Step Stacked Metamaterial

Solar absorbers are of great significance in the development of new energy technologies. However, the current approaches are mostly complex and fail to achieve high absorption rates across a wide range of wavelengths. Here, we propose a four-step stacked metamaterial solar absorber that achieves near-perfect absorption. Our four-step stacked absorber (FSSA) boasts an average absorption rate of 96.32% from 499 nm to 2348.3 nm, and a high average absorption rate of 94.96% from 300 nm to 2500 nm. Electromagnetic mode analysis and the impedance matching theory were employed to analyze the designed FSSA, which revealed that the high absorption rates are due to the propagating surface plasmon resonance (PSPR) and localized surface plasmon resonance (LSPR) modes. The FSSA offers broadband, high absorption rates, and high spectrum selectivity. Additionally, the structural parameters are adjusted to optimize the proposed perfect solar absorber. This proposed absorber can have promising applications in the renewable energy industry.

Fine periodic nanostructure formation on stainless steel and gallium arsenide with few-cycle 7-fs laser pulses

We report the fine periodic nanostructure formation process on metal and semiconductor surfaces in air with few-cycle 7-fs laser pulses and its physical mechanism. Using appropriate peak power densities and scanning speeds for the laser pulses, nanostructures could be formed on stainless steel and gallium arsenide (GaAs) with periods of 60–110 nm and 130–165 nm, respectively, which are 1/5–1/4 of the period of nanostructures formed with 100-fs laser pulses. The periodicity can be explained as arising from the excitation of short-range propagating surface plasmon polaritons, and the observed periods are in good agreement with the model calculation results.

Tailoring surface plasmon wave based on natural hyperbolic dispersion of black phosphorus

The unique transport behavior of surface plasmons confined in the xy-plane is explored using different transition frequencies for different crystallographic axes of black phosphorus (BP). Electromagnetic simulations reveal that the proportion of intraband and interband electron motion within the two-dimensional (2D) BP governs the propagation state of surface plasmons. We illustrate the topological transformation in the dispersion curve of 2D BP that can lead to changes in the surface plasmon propagation state. Moreover, the different dispersion relations have been tuned by changing the electron doping concentration of 2D BP that can be applied to manipulate the propagation direction of surface plasmons. Our design offers a promising platform for plasma control applications in the field of optics.

Surface Plasmon Polaritions via Squeezed Vacuum States

This paper investigates a dielectric under a squeezed vacuum state, a thermal field and a normal vacuum state. The dielectric atoms are considered in a three-level lambda type configuration, where a weak probe field induces and generates surface plasmon polaritons (SPPs) at the silver and dielectric interface. Therefore, to get deeper insights into the dispersion and absorption spectra, the propagation length and the skin depth, we investigate the system’s coherence. Hence, we demonstrate that the strong laser used to couple the intermediate level to the upper excited state drastically affects the generated SPPs wavelength at the interface. Additionally, the system properties are fully controlled by the average photon number, the thermal field, the normal vacuum and the squeezed vacuum state. Finally, in an attempt to elaborate a straightforward technique that manipulates the Lsp ( surface plasmon length ) distance we control the system by simultaneously tuning the phase and the control field in a particular detuning region. Our results might be of great interest to the engineering of miniature nano-photonic devices and circuits requiring sub-wavelength property.

Design of an ultra-wideband solar absorber based on tungsten

A solar absorber based on tungsten with an ultra-wide wavelength band is investigated numerically using the finite-difference time–domain method. The designed structure consists of a cross-shaped resonator on top of the absorber and a metal thin film on the bottom that are separated by an intermediate dielectric layer. The absorber demonstrates continuous high absorptivity (>90%) over the 514–1945 nm wavelength range, and the average absorptivity ranges up to 92.36% within the 200–2000 nm range. The excitation of propagating surface plasmon resonance (SPR) and localized SPR in combination with Fabry–Pérot resonance leads to the observed wideband absorption. We also demonstrate that the proposed absorber is insensitive to both transverse electric and transverse magnetic polarizations and study its absorptive performance at larger angles of incidence. The effects of the structural parameters and of different dielectric layer materials on the absorption performance have also been investigated. Furthermore, we explain the absorption mechanism using a power flow plot and impedance matching. The proposed absorber has promising prospects for applications, including solar cells, solar energy harvesting, and thermal emitters.

(Invited) Dynamics of Light-Matter Interactions in Plasmonic Optical Cavities for Characterizing Nanostructures Relevant to Energy Conversion and Photocatalysis

Optical cavities are an established means to increase light-matter interactions with a wide range molecules, nanostructures and bulk materials. The use of an optical cavity to increase the likelihood of photon absorption by a material has clear potential for being of value for optical energy conversion and photocatalysis. Furthermore, optical cavities can significantly alter excited state dynamics due to the potential for Purcell effects that increase radiative rates of emission of a given material, molecule, or nanostructure. These dynamic changes can serve as a sensing mechanism of cavity impact to photoprocesses, making characterization tools such as transient absorption and time-resolved emission measurements an effective means to probe the degree of light-matter coupling. Taken a step further, these characterization tools can help establish the degree of light-matter coupling necessary to control excited state lifetimes for a particular purpose or application. Here, we explore the dynamics of nanostructured systems coupled to, or made out of, plasmonic materials. Importantly, plasmonic structures are well-known to serve as a type of optical cavity, and though plasmonic cavities are lossier than their dielectric counterparts, they can also confine light to a small mode volume which is very helpful for increasing photonic interactions with nanostructures. The focus of this talk is on materials and nanostructures of interest for solar energy conversion or photocatalysis, such plasmonic nanoparticles and semiconducting nanoparticles, which are interacting with or functioning as, a plasmonic cavity. The plasmonic cavity can be as simple as a thin metal film that supports a propagating surface plasmon polariton (SPP). We also explore refractory plasmonic systems due to their potential durability and reduced likelihood of melting under optical illumination as compared to noble metal nanostructures. The dynamics of nanostructure photoprocesses as a function of photon energy relative to the cavity resonance is explored in detail and impact on applications is described. Work performed at the Center for Nanoscale Materials, a U.S. Department of Energy Office of Science User Facility, was supported by the U.S. DOE, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.

Numerical Study of Silicon and Tungsten Diselenide Nanomaterial‐Based Surface Plasmon Resonance Sensor for Refractive Index Sensing

A Kretschmann configuration‐based surface plasmon resonance sensor is proposed. The sensor is made up of calcium fluoride prism, silver, silicon, and tungsten di selenide nanolayer. The theoretical and numerical study of surface plasmon resonance sensor is analyzed by angle interrogation method with the help of MATLAB 2017b. The transfer matrix method (TMM) is the foundation for simulation and a monochromatic light of wavelength 633 nm is considered as source. In the proposed device structure, each layer is arranged in vertical format to improve the electrical and optical properties. The refractive index for analyte is considered as 1.330 to 1.335. Silver (Ag) metal is used for the generation of surface plasmons. It has good chemical properties like metallic conductivity, chemical stability, bandgap, small work function, and acts as an adhesive layer between calcium fluoride prism and silicon layer. To improve the molecular contact and absorption, the transition metal dichalcogenide nanofilm tungsten di selenide (WSe2) is applied at the top. The sensitivity of 367.4 deg RIU−1, detection accuracy of 0.4169 deg−1, quality factor of 193.58, and full‐width half maximum of 1.8985 deg are obtained optimized performance parameters of the proposed device structure.

Surface plasmon enhanced THz spontaneous emission near metal-cored wires coated with graphene

This work deals with the theoretical study of the spontaneous emission of a point dipole source placed near a cylindrical structure composed of a central metallic core and a dielectric shell covered with graphene. We show that the spontaneous emission rate is dominated by coupling into surface plasmon (SP) modes on graphene, which present high values of the propagation constant along the cylinder symmetry axis. When the dielectric shell thickness is reduced, the plasmon dispersion is modified into a linear dependence and the modal SP propagation constant is further incremented, involving an improved field confinement. This effect is manifested as a redshift of the emission frequency spectrum for each individual cylindrical harmonic mode. We propose a simple model that provides us a link between the dispersion characteristics and maximum emission rate for each SP cylindrical mode.

Correlation between plasmon lifetime and near-field enhancement in nanoparticle-on-film systems

Lifetime and near-field enhancement of coupled plasmonic systems have attracted increasing attention in recent years. However, the relationship between them in the coupled plasmon structure has not been systematically revealed. Here, we studied the correlation between the plasmon lifetime and near-field enhancement of the plasmonic gap mode of nanoparticle-on-film systems, which associates localized surface plasmons with propagating surface plasmons. Both proportional and inversely proportional relationships between lifetime and field enhancement can be achieved by tuning the system parameters. The lifetime can be modulated from 5.4 fs to 20.5 fs, with the near-field intensity enhancement changing from 1036-fold to 9960-fold. Furthermore, it is found that the extension of lifetime is influenced by film thickness and limited by the skin depth of 42 nm, and the near-field enhancement of the system is mostly determined by the coupling efficiency of propagating surface plasmons.

A near-perfect metamaterial selective absorber for high-efficiency solar photothermal conversion

High-efficiency solar metamaterial selective absorbers are indispensable technologies for new renewable energy, with significant application prospects in realizing high-efficiency solar photothermal and photoelectric conversion and desalination. Although various solar selective absorbers have been achieved, there are generally problems such as low efficiency, complex structure, and poor spectral selectivity. Herein, we propose a dual-dielectric-layer metamaterial selective absorber (DDMSA) that achieves near-perfect absorption in the entire solar spectrum while having low thermal radiation in the mid-infrared region. The proposed DDMSA can achieve strong absorption with an absorbance of above 90% over a wide spectrum from ultraviolet to near-infrared (i.e., from 280 to 2280 nm). This broadband strong absorption is attributed to several mechanisms, including interference effects, localized surface plasmon resonance (LSPR), propagating surface plasmon resonance (PSPR), and intrinsic losses of tungsten. An impressive solar photothermal efficiency surpassing 90% has been achieved spanning a broad temperature range from 100 to 1000 °C. Notably, it possesses superior performance in polarization-independent and wide-angle incidence behaviors. Therefore, the proposed metamaterial selective absorber has great potential in applications related to solar photothermal harvesting.

Broadband ultra-thin Long-Wave InfraRed metamaterial absorber based on trapezoidal pyramid array

The ultra-thin absorber in the long-wave infrared band plays an important role in imaging, sensor, and energy collection. Various perfect absorbers in the long wave infrared band have been designed, however, the absorption bandwidth and structural thickness still limit their application. Here, we propose an ultra-thin perfect absorber composed of a periodic Ti trapezoidal pyramid array, on GaAs dielectric spacer layer, with Ti reflection substrate. Due to the excitation of propagating surface plasmon resonance and local surface plasmon resonance, the average absorptivity about 93.6% in the 8–15 μm band is obtained, which is insensitive to the polarization angle and incidence angle. The resonance characteristics of the structure are studied through the electrostatic theory, and the broadband absorption properties for varied geometric parameters are analyzed using the multipole decomposition method. Meanwhile, we achieved the absorptivity more than 90% at 9.1–17.1 μm by changing the dielectric spacer layer structure of the absorber, and the average absorptivity is 92.1%.

Spectrum enhancement of extraordinary terahertz transmission through metal-dielectric multilayer compound annular hole array metamaterial

This study presents, what we believe to be, a novel approach to enhance the spectrum of extraordinary terahertz transmission utilizing surface plasmon polaritons (SPPs) mode coupling in metal-dielectric compound annular hole array metamaterial. The transmitting properties of the structure are thoroughly assessed through a combination of theoretical analysis and numerical simulation, with a particular focus on understanding the surface plasmon mode coupling. Our investigation revealed the presence of propagating surface plasmon polaritons (PSPP), localized surface plasmon resonance (LSPR) and Fabry-Perot (FP) resonances within the compound layer. We find that the coupling of PSPP and LSPR modes plays a crucial role in determining the broadband nature of the structure. Interference theory is utilized to mitigate the FP resonance, while further optimization of the transmission bands is attained by implementing the impedance matching hypothesis. By adjusting the structure parameters, the effective coupling of the SPPs modes and numerous reflections in the dielectric cavity produced a remarkably smooth and transparent character, leading to a significant enhancement of transmission spectrum and a reduction in the incident loss of terahertz wave.

Photoemission Electron Microscopy of Blue and UV Surface Plasmons on Nanostructured Aluminum Films

We image surface plasmons on aluminum surfaces in the ultraviolet and blue spectral range with photoemission electron microscopy (PEEM). Plasmon excitation is mediated by light incident on straight aluminum ridges with subwavelength cross section on flat aluminum films. We observe interference patterns due to light/plasmon interaction, with distinct periodicity and orientation depending on the light in-plane incidence angle with respect to the ridge orientation. From the interference patterns, we deduce the surface plasmon propagation directions and decay lengths. The latter are remarkably high with 2.8 μ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mu$$\\end{document}m and 8.4 μ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mu$$\\end{document}m for excitation wavelengths of 273 nm and 410 nm, respectively. Our results extend PEEM imaging of surface plasmons into the ultraviolet region.

Hyperbolic plasmons on natural biphenylene surface

Meta-surfaces constructed of patterned graphene nanoribbons on dielectric substrates have enabled in-plane propagation of surface plasmons with hyperbolic dispersion. However, the current size limitations of these meta-surface result in a restricted ceiling for the plasmon wave vector, highlighting the importance of exploring natural hyperbolic surfaces that do not require structuring. Here, we unveil a promising natural hyperbolic surface: the newly-synthesized graphene allotrope – biphenylene (BPN) [Fan et al., Science 372, 852–856 (2021)]. We demonstrate the anisotropic framework of π orbitals of BPN endows broadband hyperbolic plasmons on the BPN surface. Undamped plasmons emerge along the x-direction with a broadband spectrum from THz to the ultraviolet regime, whereas those along the y-direction are restricted to a low frequency region (<0.74 eV). Notably, hyperbolic regimes are observed within specific energy ranges, 1.21–2.44 eV and 3.35–3.51 eV, which facilitate the directional propagation of surface plasmons with hyperbolic dispersion relations. These results open an avenue for the use of graphene technique in advanced optics and offer a promising strategy for designing hyperbolic natural surfaces.

Multi-mode resonance plasmonic solar absorber based on pyramid multiary-grating

In the manuscript, a broad-band perfect absorber based on multilayer-grating and MDM film structure is proposed and numerically studied. Finite difference time domain (FDTD) simulations indicate the absorption performances are originated from Fabry–Perot (FP) resonance effect, localized, and propagating surface plasmons (LSPs and PSPs) effect. The designed absorber possesses over 95% absorption from 697 nm to 2906 nm, and an average absorption of 98.7% is achieved with TM-polarized. For TM-polarized, the designed absorber possesses over 95% between 534 nm and 2475 nm when the oblique-angle is up to 45°, while for a TE-polarized light, the corresponding average absorption remains 80.48% when the oblique-angle is up to 30°. The average absorption is larger than 94% in different environment refractive indexes (1 < RI < 1.5), which illustrates the designed absorber possesses excellent environment RI stability. Another absorber with triple layer grating of different sizes is also designed, and the absorber has more than 95% absorption between 400 nm and 2376 nm, based on the high absorption and waveband, the absorber can find potential applications in solar energy capture. It is believed the proposed work can be applied in plasmonic solar absorber design, thermal emitter, and plasmonic imaging.

Optical coupling of bio-inspired mustard protein-based bimetallic nanohybrids with propagating surface plasmon polaritons for femtomolar nitrite ion sensing: Cellphone-based portable detection device

Different classes of biologically and environmentally relevant molecules and ions are quantitatively and qualitatively analyzed using the synergistic approach wherein the properties of both the plasmonic nanomaterials and the fluorescent moieties are explored. In this study, such hybrid systems, called plasmophores (or plasmon coupled fluorophores), are investigated using the surface plasmon-coupled emission (SPCE) platform with silver, gold and silver-gold hybrid nano-structures synthesized via sustainable bio-inspired routes. A simple, rapid, user-friendly and green chemistry approach has been adopted using biocompatible mustard protein as both the reducing and capping agent during nanosynthesis. The morphologically and functionally tunable plasmonic nanomaterials were synthesized by simply exposing a mixture of the respective metal ions and protein to UV-light irradiation. Comprehensive analysis of the out-coupled spontaneous emission in the SPCE framework using spacer, cavity and extended cavity nanointerfaces yielded intriguing results, presenting optimum prerequisites for realizing high SPCE enhancements. More than a 950-fold improvement in the fluorescence signal intensity of rhodamine B was demonstrated utilizing the plasmonic cavity hotspots rendered by the hybrid coupling of the propagating surface plasmon polaritons of Ag with localized plasmon resonances of the bimetallic AgAu nanohybrids. The sharply directional and highly polarized SPCE enhancements, realized without increasing the illumination intensity, were utilized for quantitative detection of biologically relevant nitrite ions in drinking water samples at trace concentrations (limit of detection: 0.1 femtomolar). The applicability and relevance of the demonstrated method for sustainable use of plasmonic nanomaterials in photo-plasmonic research is presented by accomplishing the sensing using a cost-effective smartphone camera with a good correlation with the data obtained from a conventional detector system. Hence, the bio-nano-inspired strategy described here reveals several potential opportunities for the development of environmentally benign portable chemosensing devices for utility in academia and industry, especially for low-and-middle income countries.

Effect of fatty acid’s dielectric constant in the generation of surface plasmons using numerical attenuated total reflection (ATR)

The surface plasmons were collective excitation of free charges which can be generated at the interface between metal and dielectrics. The active material was metal which provided free charges while dielectrics was passive material which maintained the electric fields at the interface. One of the most effective method to generate surface plasmons was attenuated total reflection (ATR). The basic concept of this method was total internal reflection. Hence, it required a high index prism, such as thallium halogenide. The ATR method can be done numerically by deriving ATR reflectivity. In the process of derivation, we should consider the reflectivity at the all involved interfaces. Then, the ATR reflectivity can be obtained by scanning frequency at the certain interval near the surface plasmon frequency. In this report, we study the surface plasmon which was generated at the interface between gold and fatty acid. We analysed the effect of fatty acid’s dielectric constant to the ATR spectroscopy. We found that the decrease of the fatty acid’s permittivity increase the surface plasmon resonance (SPR frequency and decrease the reflectivity at this resonance frequency.