Interaction Of Surface Plasmons Research Articles

Pongamia pinnata seed extract-mediated green synthesis of silver nanoparticle loaded nanogel for estimation of their antipsoriatic properties.

This research describes the eco-friendly green synthesis of silver nanoparticles employing Pongamia pinnata seed extracts loaded with nanogel formulations (AgNPs CUD NG) to improve the retention, accumulation, and the penetration of AgNPs into the epidermal layer of psoriasis. AgNPs were synthesized using the Box-Behnken design. Optimized AgNPs and AgNPs CUD NG were physico-chemically evaluated using UV-vis spectroscopy, SEM, FT-IR, PXRD, viscosity, spreadability, and retention studies. It was also functionally assessed using an imiquimod-induced rat model. The entrapment efficiency of AgNPs revealed ~ 79.35%. Physico-chemical parameters announced the formation of AgNPs via surface plasmon resonance and interaction between O-H, C = O, and amide I carbonyl group of protein extract and AgNO3. Optimized AgNPs showed spherical NPs ~ 116nm with better physical stability and suitability for transdermal applications. AgNPs CUD NG revealed non-Newtonian, higher spreadability, and better extrudability, indicating its suitability for a transdermal route. AgNPs CUD NG enhanced the retention of AgNPs on the psoriatic skin compared to normal skin. Optimized formulations exhibit no irritation by the end of 72h, indicating formulation safety. AgNPs CUD NG at a dose of 1 FTU showed significant recovery from psoriasis with a PASI score of ~ 0.8 compared to NG base and marketed formulations. Results indicated that seed extract-assisted AgNPs in association with CUD-based NG formulations could be a promising nanocarrier for psoriasis and other skin disorders.

Defocused imaging-based quantification of plasmon-induced distortion of single emitter emission

Optical properties of single emitters can be significantly improved through the interaction with plasmonic structures, leading to enhanced sensing and imaging capabilities. In turn, single emitters can act as sensitive probes of the local electromagnetic field surrounding plasmonic structures, furnishing fundamental insights into their physics and guiding the design of novel plasmonic devices. However, the interaction of emitters in the proximity to a plasmonic nanostructure causes distortion, which hinders precise estimation of position and polarization state and is one of the reasons why detection and quantification of molecular processes yet remain fundamentally challenging in this era of super-resolution. Here, we investigate axially defocused images of a single fluorescent emitter near metallic nanostructure, which encode emitter positions and can be acquired in the far-field with high sensitivity, while analyzing the images with pattern matching algorithm to explore emitter-localized surface plasmon interaction and retrieve information regarding emitter positions. Significant distortion in defocused images of fluorescent beads and quantum dots near nanostructure was observed and analyzed by pattern matching and finite-difference time-domain methods, which revealed that the distortion arises from the emitter interaction with nanostructure. Pattern matching algorithm was also adopted to estimate the lateral positions of a dipole that models an emitter utilizing the distorted defocused images and achieved improvement by more than 3 times over conventional diffraction-limited localization methods. The improvement by defocused imaging is expected to provide a way of enhancing reliability when using plasmonic nanostructure and diversifying strategies for various imaging and sensing modalities.

THE INFLUENCE OF A POTENTIAL BARRIER ON THE MECHANISMS OF EXCITATION OF OWN FLUCTUATIONS IN RADIO PRODUCTS IN CONDITIONS OF EXPOSURE TO ELECTROMAGNETIC RADIATION

The subject matter is the processes of analysis and the mechanisms of the emergence of their own fluctuations in the semiconductor complex electro -radio devices (communications equipment), if there are currents and voltages entrusted with pulsed electromagnetic radiation, the results obtained in the work of the potential barrier on the border of the semi -conductive structure on the border of the semiconductor (voltage ampere) characteristics of a electro -radio device. The aim is model of transforming the energy of the flow of charged particles, induced by external electromagnetic radiation, into the energy of its own fluctuations in the semiconductor structure, taking into account the properties of the structure itself (heterogeneity of potential at the border). The implementation of this model is due to the effect of transitional radiation of moving charges, when the particle flow crosses the boundary of the media section with various electromagnetic properties (dielectric permeability) and part of its energy is transformed into the energy of its own fluctuations in the semiconductor structure. The objectives are: mechanisms of the strengthening (instability) mode of semiconductor components of semiconductor devices under conditions of impulse electromagnetic radiation in the presence of a potential barrier on the boundary of the media of the media. The methods used are the method of theory of small disturbances, which allows you to determine the spectrum of the own vibrations of the system: the current fluctuations of the semiconductor device in electromagnetic radiation. The following results are obtained: The interaction of surface plasmons with the flow was considered charged particles in the presence of a potential barrier based on energy principle. Kinetic equations have been obtained that determine the change in the number superficial plasmons, expressions for the increments of their instability with taking into account the size of a potential barrier on the border, which leads to the appearance of a beam reflected from the border. The results of the work allow you to take into account the contribution of the reflected and completed component of the energy flow energy into the total energy of the radiation of surface vibrations. The mechanisms of interaction between the flow of charged particles with the own electromagnetic fluctuations of two -dimensional electronic gas, the occurrence of which is due to the presence of a potential barrier on the border of the media section. Conclusion. Determination of the amplification (generation) modes of electro -radio products that distort their volt are ampere characteristics (reversible failures) depending on the parameters of external electromagnetic radiation. An analysis of the routes obtained in the work can be used in the development of radio emergency for working in a millimeter and submilimeter range (amplifiers, generators and frequency converters). Assessment of indicators of the exponential growth of amplitudes of the own fluctuations of semiconductor components (increement of instability as a criterion of reversible failures) show that the magnitude of the energy of radiation lies within the sensitivity of modern receivers of the radiation of the submilimeter range and is the reason for the failure.

Terahertz inner and outer edge modes in a tetramer of strongly coupled spoof localized surface plasmons.

Photonic edge mode confining light in cavities of surface plasmons is beneficial in image and biosensor applications. In the terahertz band, however, the edge mode in a cavity of spoof localized surface plasmons has not matured sufficiently. Herein, a cost-effective strategy to achieve a terahertz photonic edge mode using a metasurface of strongly coupled fourfold spoof localized surface plasmons in a tetramer layout is demonstrated. The quality factors of edge modes decrease when the tetramer shrinks, as revealed by the terahertz dielectric functions. The edge modes that emerge can be categorized as inner and outer edge modes, as deduced from the simulated electric field distribution. Our results show that the edge modes are due to the interaction of spoof localized surface plasmons in the terahertz band.

Modulation of Casimir Force between Graphene-Covered Hyperbolic Materials

A flexible method for modulating the Casimir force is proposed by combining graphene and hyperbolic materials (HMs). The proposed structure employs two candidates other than graphene. One is hexagonal boron nitride (hBN), a natural HM. The other is porous silicon carbide (SiC), which can be treated as an artificial HM by the effective medium theory. The Casimir force between graphene-covered hBN (porous SiC) bulks is presented at zero temperature. The results show that covering HM with graphene increases the Casimir force monotonically. Furthermore, the force can be modulated by varying the Fermi level, especially at large separation distances. The reflection coefficients are thoroughly investigated, and the enhancement is attributed to the interaction of surface plasmons (SPs) supported by graphene and hyperbolic phonon polaritons (HPhPs) supported by HMs. Moreover, the Casimir force can be controlled by the filling factor of porous SiC. The Casimir force can thus be modulated flexibly by designing desired artificial HMs and tuning the Fermi level. The proposed models have promising applications in practical detection and technological fields.

Studies on plasmon coupling between pure colloidal gold nanoparticles prepared by laser ablation in water

Localized surface plasmon interaction of colloidal gold nanoparticles and the resultant changes in the linewidth of plasmon bands are reported. The evolution of the plasmon band in colloids is investigated by increasing the number of particles per unit volume. The volume of the solvent is reduced from 15 to 3 ml by the simple evaporation method. It is observed that the linewidth of the plasmon band varies in a non-uniform manner, which is attributed to the interaction of plasmons from the surface of gold nanoparticles rather than aggregation effects. Indication of aggregation effects such as a progressive redshift in plasmon peak and continuous broadening of linewidth were absent. Gold nanoparticles are prepared using laser ablation of the gold target with nanosecond laser pulses using pure water as a solvent. Change in the linewidth of plasmon bands on colloidal gold nanoparticles with minimized size distribution prepared using laser fluences viz. 5.09, 10.19, 15.28, 20.38 and 25.48 J/cm2 are explored.

Adiabatic mode transformation in width-graded nano-gratings enabling multiwavelength light localization

We delineate the four principal surface plasmon polariton coupling and interaction mechanisms in subwavelength gratings, and demonstrate their significant roles in shaping the optical response of plasmonic gratings. Within the framework of width-graded metal–insulator-metal nano-gratings, electromagnetic field confinement and wave guiding result in multiwavelength light localization provided conditions of adiabatic mode transformation are satisfied. The field is enhanced further through fine tuning of the groove-width (w), groove-depth (L) and groove-to-groove-separation (d). By juxtaposing the resonance modes of width-graded and non-graded gratings and defining the adiabaticity condition, we demonstrate the criticality of w and d in achieving adiabatic mode transformation among the grooves. We observe that the resonant wavelength of a graded grating corresponds to the properties of a single groove when the grooves are adiabatically coupled. We show that L plays an important function in defining the span of localized wavelengths. Specifically, we show that multiwavelength resonant modes with intensity enhancement exceeding three orders of magnitude are possible with w < 30 nm and 300 nm < d < 900 nm for a range of fixed values of L. This study presents a novel paradigm of deep-subwavelength adiabatically-coupled width-graded gratings—illustrating its versatility in design, hence its viability for applications ranging from surface enhanced Raman spectroscopy to multispectral imaging.

High Performance Plasmonic Nano-Biosensor Based on Tunable Ultra-Narrowband Perfect Absorber Utilizing Liquid Crystal

In this paper, a refractive index plasmonic nano-sensor based on a tunable perfect absorber has been proposed in the near-infrared region. The proposed sensor consists of a truncated cone resonator with more than 99% absorption and ultra-narrow bandwidth. Liquid crystal has been used in the designed nano-structure to tune the structure by variation of the incident angle and applying the external bias field to obtain the near perfect and ultra-narrow absorption peak. The proposed nano-sensor has a high sensitivity of 1363.63 nm/RIU and a high figure of merit of 1136.36 RIU−1 at the telecommunication wavelength of 1550 nm. Furthermore, after obtaining appropriate conditions for the liquid crystal layer, we have suggested a new resonator to boost the interaction of surface plasmons and the test medium. Therefore, the sensitivity and figure of merit are increased to the values of 1509 nm/RIU and 1257.5 RIU−1, respectively. This excellent performance of the sensor has huge potential for precision applications such as biomedical science and biosensor. Hence, the capability of the proposed nano-sensor in the field of histopathology for cancerous tissue diagnosis and detection of toxic and flammable gases to prevent endangering human health has been studied. In this case, the high sensitivity of 1368.06 nm/RIU and high figure of merit of 1179.36 RIU−1 have been obtained.

Tip-Based Plasmonic Nanofocusing: Vector Field Engineering and Background Elimination

Nearly thirty years ago, Specht et al. proposed a new optical near-field microscope based on the interaction of surface plasmons and a sharp metal tip. Since then, the tip-based plasmonic nanofocusing has been widely studied. When the tip-based plasmonic nanofocusing integrated with scanning probe microscopy, it not only forms highly localized enhanced electric field to boost the spectral signal but also simultaneously provides morphological information. These amazing properties provide a new detection method to understand the nano-world, including spatial structures of chemicals and physical, electronic and catalytic properties of substance. Upon growing demand for background-free nanofocusing, more and more attention is being drawn to developing new technologies for it. Hitherto, owing to the salient properties, tip-based background-free nanofocusing have tremendous advanced applications such as ultrafast optics, nonlinear optics, and even electron emission. This article reviews the historical developments from fundamentals to the techniques for tip-based plasmonic nanofocusing and then to their advanced applications.

Förster Resonance Energy Transfer and Molecular Fluorescence near Gain Assisted Refractory Nitrides Based Plasmonic Core-Shell Nanoparticle

The process of Forster resonance energy transfer (FRET) and molecular fluorescence (MF) plays a vital role in protein–protein interaction, detection of nucleic acids, photochemistry, molecular spectroscopy, forensics, fingerprinting, photovoltaics, etc., to name only a few. The present work focus on developing closed form expressions for FRET enhancement, fluorescence yield (FY), and quantum yield (QY) in the presence of core-shell nanoparticle (CSNP) consisting of dielectric core and metallic shell. It is shown that the plasmonic nanoparticle enhance the FRET significantly only when the donor and acceptor molecules are far apart. When both molecules are closely placed (~ 1 nm), plasmonic nanoparticle does not enhance the FRET significantly. Therefore, when acceptor–donor molecules of chromophore are closely placed, significant FRET enhancement cannot be realized via molecule–surface plasmon interaction. The present work shows that this problem can be resolved by incorporating optical gain in the dielectric core of CSNP, and this is an effective mechanism for enhancing molecular interaction when donor–acceptor molecules are closely placed. In addition to FRET, molecular fluorescence in the presence of CSNP is also studied. The well-established Gersten-Nitzan model is extended to derive closed form expressions for FRET, FY, and QY, albeit near core-shell nanoparticle. Notably, gigantic enhancement in FRET and FY by virtue of loss compensation is accompanied by reduction in resonance linewidth. Refractory nitrides (e.g., ZrN and TiN) based CSNPs are assessed for their feasibility in enhancing FRET, and FY and performance comparison with Au is also presented.

Heating Effects on Optical Properties of Metal Nano Particle

Localized Surface Plasmon (LSPR) occurs on the interface of Metal Nano Particle (MNP) when illuminated with electromagnetic wave, at a specific electromagnetic energy (wavelength). In this work, we model the gold nanoparticle (AuNP) composite by its atomic polarizability, that is related to the absorption, and its dependence on temperature. To compare the resulted LSPR frequency shift when the AuNP system is heated, we synthesized the MNP composite of polymer (oleylamine) capped gold nanoparticle (AuOA) and measured the optical properties which is related to the LSPR resonance frequency through the atomic polarizability of the composite. The temperature dependence effect is observed by depositing the AuAO onto a thin film after mixing with a polymer solvent (P3HT : PCBM) and heating it. It is found that a perceptible blueshift of the LSPR signal is observed which is contrary to the prediction from the model. This effect can be attributed to the thermal expansion of the thin films due to the heating process. After heating, the relative distance between two nanoparticles becomes larger, thus the weakening of surface plasmon interaction between the particles.

Modulation of THz radiation via enhanced Dirac plasmon-dual phonon interaction

Imaging with terahertz (THz) radiation is a crucial technique that promotes its applications in security inspection, crack detection, biomedical imaging, and so forth. THz modulation is one of the critical factors (others include generation, propagation, and detection) of the THz fast imaging technique. In this work, an efficient THz radiation modulator is realized based on the as-grown Bi2Se3 nanowires. Different from the conventional metamaterials or plasmonic devices, fabrication of subwavelength structures is unnecessary in this manipulation. The modulation is facilitated via synergistic Fano-type interaction of topological surface plasmons with two phonons in Bi2Se3 nanowires. The comprehensive control of the modulation is realized in a direct optical manner. A high modulation depth of 1826% has been demonstrated in this modulator. The realization of such a THz modulator based on an as-grown system indicates the possibility of the modulation extricating from fabrication of complicated postgrowth micro/nanostructures.

Multiple Fano resonances in spoof plasmon resonators of corrugated cylinder/ring structure

We theoretically investigate the spoof surface plasmon interactions in a composite structure consisting of a corrugated metal cylinder and a grooved ring. We demonstrate that the corrugated cylinder can support multipolar sharp cylinder-like resonances, while the grooved ring can support broad-band cavity-like resonances. These two kinds of spectrally overlapping resonances can interfere and result in multiple Fano resonances in the THz regime. We also demonstrate that the introduction of a defect into the corrugated cylinder can generate more Fano interference features. We hope these multiple Fano resonances could be exploited for planar integrated sensing and biological detection in the THz regime.

Dark-Exciton-Mediated Fano Resonance from a Single Gold Nanostructure on Monolayer WS2 at Room Temperature.

Strong spatial confinement and highly reduced dielectric screening provide monolayer transition metal dichalcogenides with strong many-body effects, thereby possessing optically forbidden excitonic states (i.e., dark excitons) at room temperature. Herein, the interaction of surface plasmons with dark excitons in hybrid systems consisting of stacked gold nanotriangles and monolayer WS2 is explored. A narrow Fano resonance is observed when the hybrid system is surrounded by water, and the narrowing of the spectral Fano linewidth is attributed to the plasmon-enhanced decay of dark K-K excitons. These results reveal that dark excitons in monolayer WS2 can strongly modify Fano resonances in hybrid plasmon-exciton systems and can be harnessed for novel optical sensors and active nanophotonic devices.

Interaction of surface plasmon–phonon polaritons with terahertz radiation in heavily doped GaAs epilayers

We report on experimental studies of the surface plasmon-phonon polariton excitations in heavily doped GaAs epitaxial layers. Reflection and emission of radiation in the frequency range of 2–19 THz were investigated for samples with surface-relief grating, as well as for samples with planar surface. The reflectivity spectrum for p-polarized radiation measured for the sample with the surface-relief grating demonstrates a set of resonances attributed to excitations of different surface plasmon-phonon polariton modes. The observed resonances lie beyond the limits of the Reststrahlen band. Terahertz radiation emission from the samples was studied in nonequilibrium conditions under the pulsed electric field excitation. Two contributions to the spectral density of the terahertz radiation have been revealed, the first being due to bulk plasmon–phonon polaritons (PPhPs), while the second originating from the surface PPhPs. A field dependence of the effective temperature of the bulk PPhPs has been established. Polarization dependence of the terahertz radiation related to surface PPhPs has been experimentally examined for the first time.

Ultrathin MoS2 nanosheets for high-performance photoelectrochemical applications via plasmonic coupling with Au nanocrystals.

In this work, we prepared ultrathin MoS2 nanosheets with exposed active edge sites and high electric conductivity that can sufficiently absorb light in the visible region to enable solar energy conversion. The gold nanocrystal-decorated MoS2 nanosheets facilitate sufficiently enhanced photoelectrochemical water splitting in the UV-visible region. Different Au nanostructures, such as Au nanoparticles and nanorods, were modified on the surface of MoS2 nanosheets to promote photoelectrochemical water decomposition. By spin-coating a synthetic gold-modified MoS2 hybrid photoanode on a FTO substrate, the efficiency of photoelectrochemical water oxidation was significantly enhanced, by 2 times (nanorods) and 3.5 times (nanoparticles) in the visible-infrared region; furthermore, the average optical resistance was reduced by a factor of two compared to the MoS2 photoanode without Au, and the photocurrent increases exponentially when the system bias was greater than 0.7 volts. The Au-MoS2 metal-semiconductor interface plays an important role in studying the surface plasmon interactions, charge transfer mechanism, and electric field amplification. This rational design for such a unique hybrid nanostructure explains the plasmon-enhanced photoelectrochemical water splitting. This current contribution provides a new path for using the plasmonic metal/semiconductor heterostructure to effectively harvest UV-visible light for solar fuel generation.

Exploring the transfer squeezing properties from photons to symmetric and asymmetric surface plasmon polariton modes

Quantum surface plasmon polaritons (SPPs) are a growing research area with many unknown phenomena. In this paper, the behavior of squeezed SPP modes on a metal slab is assessed. To begin with, a quantized form of the SPP modes propagating on the metal thin film based on Green’s tensor method is provided. Since the squeezing properties of the SPP modes are indeed transferred from incident photons, in the next step, different aspects of this phenomenon are studied. Obtaining an important direct relation between incident photons’ properties and SPP modes will allow for the effective factors on this phenomenon to be explored. Although the initial quantum properties will be changed or lost during the photon–surface plasmon interaction, it will be shown that some factors can improve the transfer process. Finally, the squeezing transfer from incident photons to the SPP modes and effective factors on it as a full quantum phenomenon will be investigated.

Maximization of terahertz slow light by tuning the spoof localized surface plasmon induced transparency

This work numerically investigates a localized terahertz (THz) slow light phenomenon by tuning the spoof localized surface plasmon-induced transparency (PIT). A binary meta-molecule supports the interaction of the spoof localized surface plasmon (spoof-LSP), which is composed of a metallic arc and a textured circular cavity of periodic grooves. By tuning the central angle θ of the arc from 90 degrees to 170 degrees, a slow light plateau is found in the transparency window at certain frequency range. A maximum of 46 ps group delay is achieved at the θ of 135. The numerical mapping of the electromagnetic field indicates a new-born dipolar spoof-LSP that appears at the transparency windows on the circular cavity with opposite polarity to the spoof-LSP on the metallic arc. These two spoof-LSPs of opposite direction lead to a fake quadrupole, which will repel each other in magnetic dipole momentum. The slow light achieves maximum with the induced spoof-LSP and is the same as the origin spoof-LSP on the metallic arc in oscillation strength. This work paves a new way for the maximization of THz slow light.

Entanglement generation among quantum dots and surface plasmons of a metallic nanoring

We study the systems of two and three quantum dots positioned near a metallic nanoring having a surface plasmon in a particular mode. Interaction of surface plasmon with quantum dots generates entanglement between quantum dots as well as among the incident and reflected modes of the surface plasmons. We show that the maximum amount of entanglement is generated among two initially unentangled quantum dots separated by distance and with interaction parameter , while entanglement among two counter-propagating modes of the surface plasmons can be generated with interdot distance and interaction parameter , where k and μ are the propagation vector and coupling constant, respectively. In case of three quantum dots, the maximum entanglement among the quantum dots is obtained at kd = mπ/3 and Finally, the scheme is straightforwardly generalized to generate quantum entanglement among N quantum dots as well as among two counter-propagating modes of the surface plasmon due to their interactions with quantum dots.

Scintillator Light Emission Enhancement via Nanostructure and Plasmonic Design

ABSTRACTRecent work in the development of glass-ceramic scintillators at the Georgia Tech Research Institute (GTRI) has focused on modifying formulation of the oxide host glass and scintillating crystal phase, secondary heat treatment (ceramization) schedule, and processing improvement to ensure optical quality. These efforts have yielded considerable performance improvements to glass-ceramic scintillators, and have made them among the most promising composite scintillators under investigation. However, these materials still fall short of current commercially-available single crystal scintillators, and so new avenues must be pursued for continued improvements. The present investigation uses predictive simulations to inform the materials selection and process design for high refractive index layers to improve light extraction from the scintillator, and increased light output via bulk or surface plasmon interactions.