Plasmon Propagation Research Articles

Terahertz surface plasmon generation on a magnetized metal column by a rotating electron-beam

Terahertz surface plasmon generation on a magnetized metal column by a rotating electron-beam

High-efficiency terahertz surface plasmon metacoupler empowered by bilayer bright–dark mode coupling

Conversion from free-space waves to surface plasmons has been well studied as a key aspect of plasmonics. In particular, efficient coupling and propagation of surface plasmons via phase gradient metasurfaces are of great current research interest. Hereby, we demonstrate a terahertz metacoupler based on a bilayer bright–dark mode coupling structure attaining near-perfect conversion efficiency (exceeding 95%) without considering absorption loss of the materials and maintaining a high conversion level even when the area of the excitation region changes. To validate our design, a fabricated metacoupler was assessed by scanning near-field terahertz microscopy. Our findings could pave the way for developing high-performance plasmonic devices encompassing ultra-thin and compact functional devices for a diverse range of applications, especially within the realm of high-speed terahertz communications.

Surface plasmon polariton excitation and propagation in metal tripod systems

Through the activation of a planar gaseous medium consisting of four-level tripod atoms, our approach provides a mechanism to generate the Surface Plasmon Polariton (SPP). We investigate a three-layer structure in which the bottom layer is composed of atoms arranged in a tripod configuration, a metal film is layered in the middle, and a transparent layer of either air or vacuum resides on top. The bottom layer facilitates SPP excitation via amplification in the atom arrangement, caused by three laser beams: control, weak probe, and signal. The electromagnetically induced transparency effect, which can be seen in atoms, compensates for the momentum difference between light and SPP. We can coherently change SPP propagation length by altering control field strength, resonance, and off-resonant detuning. SPP optical gain power, propagation length, penetration depth, and metal thickness effects are also examined. Our method to generate SPPs may find use in lithography, sensors, polarizers, along with photodetectors.

Plasmonic sensor using generative adversarial networks integration

Machine learning (ML) has emerged as a pivotal force in enhancing the capabilities of sensing technologies across a broad spectrum of applications, from environmental monitoring and biosensing to agriculture, industrial automation, and so on. This study explores integrating ML techniques with photonic crystal fiber (PCF)-based plasmonic sensing techniques to elevate sensor performance. The PCF has two open channels to augment mode coupling, effectively reducing the gap between the analyte channel and core. Moreover, a thin layer of gold within the open channels of the PCF initiates efficient plasmon generation. The results demonstrate a maximum wavelength sensitivity of 9000 nm/refractive index unit (RIU), which can detect a wide range of analyte refractive index (RI) values from 1.33 to 1.40. The sensor exhibits the maximum amplitude sensitivity of 490.41 RIU−1. It also boasts a resolution of 1.11 × 10−5 RIU and the maximum figure-of-merit (FOM) achieved is 138.04 RIU−1 at an analyte RI of 1.39. Furthermore, this research introduces a method utilizing generative adversarial networks (GAN) to expand training data for an artificial neural network (ANN) model. This approach substantially improves the prediction of confinement loss across various analytes and wavelengths in a unique geometric configuration. The sensor’s versatility makes it ideal for various applications, including chemical sensing and medical diagnostics.

Pearcey Talbot-like plasmon: a plasmonic bottle array generation scheme.

In this Letter, a surface wave, the Pearcey Talbot-like plasmon, which has the properties of self-imaging and multiple autofocusing, is presented as a novel, to the best of our knowledge, plasmonic bottle array generation scheme. With originality, the overall structure and the partial intensity of the plasmonic bottle array can be adjusted through the initial input, and modifying the Pearcey function enables the plasmonic bottle array to exhibit self-bending characteristics, which makes particle capture and manipulation easier and more flexible. A scheme to generate the plasmon is proposed, and we prove it by the finite-difference time-domain numerical simulations.

Magnet-free electromagnetic nonreciprocity in two-dimensional materials

In this Tutorial, we overview recent developments to break and manipulate electromagnetic nonreciprocity in two-dimensional (2D) materials without relying on magnetic fields. To this purpose, we provide a general conductivity model to describe gyrotropic metasurfaces that exhibit nonreciprocity through different physical mechanisms enabled by 2D materials, including optical pumping, drifting electrons, ferromagnetic monolayers, mechanical strain, and spatiotemporal modulation. We describe in detail the resulting systems, focusing on near-field phenomena, associated to nonreciprocal bulk and edge surface plasmon propagation, and on far-field responses, related to Faraday/Kerr rotation and optical dichroism of waves propagating in free-space. Additionally, we review and contextualize recent advancements in magnet-free nonreciprocal devices based on 2D materials, ranging from Faraday rotators and optical dichrosim, to plasmonic and photonic isolators, hyperlenses, and tunable optical traps. We conclude by providing our outlook for the future development of this technology and its potential applications in areas such as communications, sensing, wave generation, and spectroscopy, among others.

Flexible plasmonic display featuring differentiated and localized control over transmission and reflection

Structural colors using metal materials, plasmonic color generation, can confine optical excitation beyond the diffraction limit owing to nanoscale metals with high efficiency in light absorption and scattering. They have several advantages over conventional display technology, including superior resolution and long-term preservation. However, most research on plasmonic color generation has been conducted for the development of static color generation, and dynamic tuning remains a challenging issue. To develop dynamic plasmonic colors, electrochemical, liquid crystal, and electromechanical methods have been proposed; however, there have been limitations in repeatability, flexibility, and scale-up processes. To address these problems, this work proposes a flexible dynamic plasmonic display using dielectric elastomer actuators (DEAs) to isotropically control the interdistance between the metal nanostructures, which can show dynamic coloration without polarization distortion. To replace the expensive and small-scale manufacturing approach, shadow masking and transfer technique with the anodic aluminum oxide (AAO) membrane was applied to realize large-scale and uniformly distributed Au nanodisc array. The differentiated and localized color change in the transmission and reflection modes, such as Janus's face, is realized by proper design of Au nanodisc array on the patterned transparent compliant electrodes formed by silver nanowires and PEDOT:PSS composites. Apparent and locally active color changes appeared in the transmission mode, but almost no color changes were observed in the reflection model by DEA actuation. The proposed system has the potential to activate color filters, cryptographic characters, and next generation display technologies.

Experimental demonstration of plasmon–plasmon scattering paves the way for electromagnetic wave-based digital logic concept

We report the experimental demonstration of plasmon–plasmon scattering at room temperature in the inversion layer of a patterned metal–oxide–semiconductor structure. This fundamental result paves the way for the development of plasmon–plasmon scattering logic, a revolutionary digital logic concept based on the generation, propagation, and manipulation of plasmons in an electron fluid, which was previously theoretically projected to exhibit femtojoule power dissipations and femtosecond switching speeds, while not demanding expensive nanometer-scale silicon (Si) technology fabrication processes for its implementation.

Terahertz Surface Plasmon Generation from Laser Interaction with a Magnetized Metallic Surface

Terahertz Surface Plasmon Generation from Laser Interaction with a Magnetized Metallic Surface

Long-range air-host plasmonic propagation with subwavelength confinement

Confining light at a subwavelength scale is important for building ultracompact opto-electronic networks. Plasmonic waveguides are good candidate devices for this purpose. However, the oscillation of electrons relating to surface plasmon polaritons causes energy dissipation, which limits the propagation length and thus reduces the waveguide performance. Here, we design a low-loss plasmonic waveguide composed of a nanowire dimer structure on a metal substrate, in which the dominant modes are localized within the air gap between the nanowires and referred to as air-host plasmonic modes. The use of air instead of dielectric materials as the host medium can reduce ohmic loss and avoid the dispersion effect of dielectric. When the constructed nanowires have a diameter less than 100 nm, the air-host mode has subwavelength-scale confinement and a propagation length of ∼100 μm, which has broad application prospects for the construction of ultracompact plasmonic devices.

Far-Field Petahertz Sampling of Plasmonic Fields.

The response of metal nanostructures to optical excitation leads to localized surface plasmon (LSP) generation with nanoscale field confinement driving applications in, for example, quantum optics and nanophotonics. Field sampling in the terahertz domain has had a tremendous impact on the ability to trace such collective excitations. Here, we extend such capabilities and introduce direct sampling of LSPs in a more relevant petahertz domain. The method allows to measure the LSP field in arbitrary nanostructures with subcycle precision. We demonstrate the technique for colloidal nanoparticles and compare the results to finite-difference time-domain calculations, which show that the build-up and dephasing of the plasmonic excitation can be resolved. Furthermore, we observe a reshaping of the spectral phase of the few-cycle pulse, and we demonstrate ad-hoc pulse shaping by tailoring the plasmonic sample. The methodology can be extended to single nanosystems and applied in exploring subcycle, attosecond phenomena.

Current-Driven Terahertz Oscillations in Diamond TeraFET

We report on sub-terahertz plasmonic wave generation in the 2DEG channel of diamond TeraFET when biased by a DC current at the drain. Our numerical results demonstrated that p-diamond can support resonant oscillation of 300 GHz at room temperature, allowing it to function as a sub-THz emitter. We investigated the impact of different channel lengths, gate biases, drift velocities, and temperatures on the fundamental mode oscillation. The model incorporated the decay factors owing to electron scattering and electron fluid viscosity.

Progress, Prospects and Challenges of MXene Integrated Optoelectronics Devices

AbstractRecently, the emerging 2D materials MXene have gained a surge of attention to the production of optoelectronics devices such as solar cells, plasmonic, phototransistors, photodetectors, light‐emitting diodes, photothermal therapy, and so on. Its outstanding optical and electrical characteristics, unique structure, and large specific surface area make it suitable for future use in modern optoelectronics including ultrafast lasers, light emitters, modulators, and plasmonic generators. There is a lack of critical analysis on the prospects, challenges, overview of synthesis methods, mechanisms, and future research directions of MXene despite having some reviews have been published on the applications of MXene. Therefore, this study critically analyzed the existing challenges of MXene, such as poor stability in an oxygen environment, inadequate mechanical properties, ease of stacking, temperature barrier, and so on. In addition, the fundamentals, preparation techniques, properties, and applications of MXene have been summarized. The mechanism, limitations, and benefits of different preparation methods have been mentioned. A comprehensive analysis and guidelines have been provided to improve the existing synthesis methods. The ways to overcome these challenges, prospects, and future markets of the MXene‐based optoelectronic devices have been described.

Phase transformation and plasmonic damping study for semi-solid ionic polymeric hydrogel system at higher temperature and low radio frequency

This article represents the findings regarding the phase transitions exhibited by a polymeric hydrogel material composed of sodium polyphosphate-polyethylene glycol. These transitions play a crucial role in the generation of ionic plasmons and the manifestation of surface plasmon resonance (SPR) with dielectric permittivity damping within the polymer electrolyte system of the hydrogel. Usually, SPR has been observed in electron-conducting systems within an optical frequency range. However, here SPR is observed in an ionic system within a lower radio frequency range of 104-10 (Parwati et al., 2024) 77 Hz for temperatures exceeding 80 °C. The mechanism responsible for permittivity damping can be elucidated by considering the accumulation of ionic charges at the interface between the electrode and the electrolyte, coupled with a high degree of charge absorption following the Drude model. A power law has been used to describe the resonance that occurs between the applied DC frequency and the motion of charge carrier ions, thus confirming the presence of free ionic motion within the hydrogel matrix. tan δ shows significant energy absorption further substantiating permittivity damping, which transitions from positive to negative values.

Biosynthesis of Silver Nanoparticles at Various pH values and their Applications in Capturing Irradiation Solar Energy.

Metallic nanoparticles (NPs), in general, are able, due to the high surface area per unit volume, to absorb the maximum incoming light flux through the vicinity of plasmonic structures and then provide local heating. Thus, silver (Ag) NPs has been used to generate heat and increase the temperature of water from solar radiation energy. The optimal plasmonic heating generation can be obtained as soon as the wavelength of the light source is close to the plasmonic resonance wavelength of Ag NPs. Ag NPs have been fabricated through a straightforward, cheap, as well as environmentally friendly approach. In this study, Salix babylonica L., weeping willow leaf extract has been utilized as a reducing, capping, and stabilizing agent, without using any other toxic materials. The importance of this study lies in the generation of hot electrons, which can be obtained by collecting the solar spectrum near the infrared and infrared regions, which cannot be obtained by the conventional photocatalytic devices. Numerous characterization techniques such as; UV-Vis, FT-IR spectroscopy, X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) analysis were used to study the optical, chemical, structural, morphological, properties of the Ag NPs. The impact of pH on the properties of Ag NPs and their performance to generate heat during solar irradiation have been investigated intensively. This study showed that the synthesized Ag NPs with pH value 12 is the optimum condition and can increase the temperature of water dramatically. An evaluation of the current patents displays that the field of green synthesis Ag NPs utilizing plant extracts is a vital field and produces rather stable, safe and effective Ag NPs. The novelty of this patent is that Ag NPs can be synthesized from a one-pot reaction without using any exterior stabilizing and reducing agent, which is not conceivable by means of the existing processes. This study, also, is rare and distinctive, and it demonstrates that even a slight quantity of the Ag NPs is significantly raising the temperature of water effectively.

Propagating surface plasmon polaritons in graphene under applied uniform strain

In this work, we theoretically investigate the propagation length of plasmon waves in graphene layer under uniform strain surrounded by two dielectric media of dielectric constants ε1 and ε2, respectively. The plasmon losses (plasmon damping), plasmon propagation length and the penetration depth of the electric field associates with the charge fluctuations can be controlled by varying the direction and the strength of the applied strain and the direction of the plasmon wave propagation with respect to the direction of the applied strain. Because strain induces anisotropy in graphene optical conductivity, the strain-dependent orientation plays an important role to manipulate the direction and variations of the graphene plasmon energy, which may be useful to tune graphene properties in plasmonic devices to enhance light-matter interaction.

Tunable Cherenkov Terahertz Graphene Surface Plasmon Generation in Graphene Sheet by a Moving Relativistic Electron Beam

Tunable Cherenkov Terahertz Graphene Surface Plasmon Generation in Graphene Sheet by a Moving Relativistic Electron Beam

Light-Emitting Plasmonic Tunneling Junctions: Current Status and Perspectives.

Quantum tunneling, in which electrons can tunnel through a finite potential barrier while simultaneously interacting with other matter excitation, is one of the most fascinating phenomena without classical correspondence. In an extremely thin metallic nanogap, the deep-subwavelength-confined plasmon modes can be directly excited by the inelastically tunneling electrons driven by an externally applied voltage. Light emission via inelastic tunneling possesses a great potential application for next-generation light sources, with great superiority of ultracompact integration, large bandwidth, and ultrafast response. In this Perspective, we first briefly introduce the mechanism of plasmon generation in the inelastic electron tunneling process. Then the state of the art in plasmonic tunneling junctions will be reviewed, particularly emphasizing efficiency improvement, precise construction, active control, and electrically driven optical antenna integration. Ultimately, we forecast some promising and critical prospects that require further investigation.

Review of Gold Nanoparticles in Surface Plasmon-Coupled Emission Technology: Effect of Shape, Hollow Nanostructures, Nano-Assembly, Metal-Dielectric and Heterometallic Nanohybrids.

Point-of-care (POC) diagnostic platforms are globally employed in modern smart technologies to detect events or changes in the analyte concentration and provide qualitative and quantitative information in biosensing. Surface plasmon-coupled emission (SPCE) technology has emerged as an effective POC diagnostic tool for developing robust biosensing frameworks. The simplicity, robustness and relevance of the technology has attracted researchers in physical, chemical and biological milieu on account of its unique attributes such as high specificity, sensitivity, low background noise, highly polarized, sharply directional, excellent spectral resolution capabilities. In the past decade, numerous nano-fabrication methods have been developed for augmenting the performance of the conventional SPCE technology. Among them the utility of plasmonic gold nanoparticles (AuNPs) has enabled the demonstration of plethora of reliable biosensing platforms. Here, we review the nano-engineering and biosensing applications of AuNPs based on the shape, hollow morphology, metal-dielectric, nano-assembly and heterometallic nanohybrids under optical as well as biosensing competencies. The current review emphasizes the recent past and evaluates the latest advancements in the field to comprehend the futuristic scope and perspectives of exploiting Au nano-antennas for plasmonic hotspot generation in SPCE technology.

Influence of molecular structure on the coupling strength to a plasmonic nanoparticle and hot carrier generation.

Strong coupling between metal nanoparticles and molecules mixes their excitations, creating new eigenstates with modified properties such as altered chemical reactivity, different relaxation pathways or modified phase transitions. Here, we explore excited state plasmon-molecule coupling and discuss how strong coupling together with a changed orientation and number of an asymmetric molecule affects the generation of hot carriers in the system. We used a promising plasmonic material, magnesium, for the nanoparticle and coupled it with CPDT molecules, which are used in organic optoelectronic materials for organic electronic applications due to their facile modification, electron-rich structure, low band gap, high electrical conductivity and good charge transport properties. By employing computational quantum electronic tools we demonstrate the existence of a strong coupling mediated charge transfer plasmon whose direction, magnitude, and spectral position can be tuned. We find that the orientation of CPDT changes the nanoparticle-molecule gap for which maximum charge separation occurs, while larger gaps result in trapping hot carriers within the moieties due to weaker interactions. This research highlights the potential for tuning hot carrier generation in strongly coupled plasmon-molecule systems for enhanced energy generation or excited state chemistry.