Plasmonic Devices Research Articles

Extremely Stable Ag-Based Photonics, Plasmonic, Optical, and Electronic Materials and Devices Designed with Surface Chemistry Engineering for Anti-Tarnish.

Silver (Ag) metal-based structures are promising building blocks for next-generation photonics and electronics owing to their unique characteristics, such as high reflectivity, surface plasmonic resonance effects, high electrical conductivity, and tunable electron transport mechanisms. However, Ag structures exhibit poor sustainability in terms of device performance because harsh chemicals, particularly S2- ions present in the air, can damage their structures, lowering their optical and electrical properties. Here, the surface chemistry of Ag structures with (3-mercaptopropyl)trimethoxysilane (MPTS) ligands at room temperature and under ambient conditions is engineered to prevent deterioration of their optical and electrical properties owing to S2- exposure. Regardless of the dimensions of the Ag structures, the MPTS ligands can be applied to each dimension (0D, 1D, and 3D). Consequently, highly sustainable plasmonic effects (Δλ < 2nm), Fabry-Perot cavity resonance structures (Δλ < 2nm), reflectors (ΔRReflectance < 0.5%), flexible electrodes (ΔRelectrical < 0.1 Ω), and strain gauge sensors (ΔGF < 1), even in S2- exposing conditions is achieved. This strategy is believed to significantly contribute to environmental pollution reduction by decreasing the volume of electronic waste.

Modulating Polarization in Second Harmonic Generation through Symmetry Evolution in Plasmonic Lattices.

We report a strategy for preparing cost-effective plasmonic square lattices with tunable unit structures of circles, crosses, and circle-cross pairs on a centimeter scale. The asymmetrical electromagnetic (EM) field distribution of the lattice enhances second harmonic generation (SHG) under oblique incidence. The SHG signals are progressively strengthened as the unit symmetry decreases from C∞v (circle) to C4v (cross) to C2v (circle-cross pair). The peak SHG signal is observed from the plasmonic lattice with a circle-cross pair, showcasing a conversion efficiency of 1.0 × 10-2, which is a 7.3-fold enhancement relative to the dielectric lattice comprised of circle units. This notably high conversion efficiency of SHG is on par with that of phase-matched bulk nanostructures under normal incidence, benefiting from the Bloch-surface plasmon polariton (Bloch-SPP) modes associated with the distribution of the photonic local density of states (LDOS). Furthermore, the SHG emission exhibits distinctive directional and polarization characteristics as the unit symmetry is reduced. This work offers valuable insights into a structural symmetry-dependent SHG in plasmonic lattices and the way forward for the design of functional nonlinear plasmonic devices.

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.

Impact of Hybrid Plasmonic and Temperature in Random Laser Tuning

This research explores the interaction between silver films and dispersed silver nanowires (Ag NWs) in the context of generating random laser emission. To achieve random lasing, we use a mixture of Rhoda mine B (RhB) dye and a polyvinyl alcohol (PVA) matrix as the gain medium. The combination of silver components plays a crucial role in trapping and controlling light. The surface characteristics of the film, including its roughness and the interplay between localized and extended surface plasmons significantly affect the performance of the random laser (RL). The laser’s threshold is closely linked to the thickness of the film, which is influenced by its surface roughness. Additionally, variations in film thickness lead to wavelength modulation, ranging from 597 nm to 606 nm, primarily due to the reabsorption of RhB. Moreover, this research demonstrates the intriguing capability to tune emission wavelengths in response to temperature changes, promising precise wavelength control for plasmonic devices and potential applications.

High-efficiency light manipulation using a single layer of folded graphene microribbons

Since its one-atom thickness, it remains an open question to enhance light–matter interactions in graphene, which is usually implemented through external resonant structures such as Fabry–Perot cavity. Here, we propose an alternative scheme to enhance light–matter interactions in a single layer of folded graphene microribbons (FGMRs), and remarkably, for normal incidences rather than oblique incidences in most studies. By optimizing structural parameters (e.g., the location of folding axis and folding angle), three light manipulations such as perfect absorption, perfect reflection, and perfect transmission can be achieved independently. More interestingly, any one of the three functionalities can be actively switched to the other via changing material parameters (Fermi level and carrier mobility ), which is actually the most attractive feature of graphene plasmonics. Finally, we show FGMRs can also support triple functionalities, i.e., via changing material parameters, one of the three functionalities can be switched to the second one and then the third one. Our results will be of great interest to fundamental physics and pave the way for graphene plasmonic device applications.

Monolithic Electrically‐Driven Retroreflector Based on Gold Nanoparticles Embedded in Ferroelectric Polymer

The surface plasmon resonance (SPR) observed in metal nanostructures finds application in biosensing, optical communication technologies, and neuromorphic computing. There it enables the detection and transduction of dielectric environment changes in the vicinity of the metal nanostructure. Combining this principle with materials where the dielectric environment can be electrically modulated, it becomes possible to realize active optoelectronic plasmonic devices specifically designed for optical communication technologies. In this work, the use of an organic ferroelectric polymer to reversibly modulate the localized SPR (LSPR) of gold nanoparticles (AuNPs) inducing a reversible spectral shift of the resonance is investigated. The proposed plasmonic modulator is based on a two‐terminal device composed of AuNPs deposited on a transparent conductive electrode, covered by a ferroelectric polymer poly(vinylidene fluoride‐co‐trifluoroethylene) with a metallic electrode on top also serving as the mirror. By applying a voltage bias between the two electrodes, an electric field is generated within the device, enabling precise control over the dielectric environment of the AuNPs and thereby modulating the LSPR. It is demonstrated that this concept can be easily fabricated, potentially flexible, lightweight, and robust, making it an attractive choice for optical communication devices, particularly as a free space modulating retroreflector.

Electromechanically reconfigurable plasmonic nanoslits for efficient nano-opto-electro-mechanical tuning

Plasmonic metamaterials with strong localized surface plasmon resonances (LSPRs) have been improved by incorporating a nano-opto-electro-mechanical system (NOEMS) for tunable optical and electrical responses. However, conventional NOEMS devices suffer from the inefficient free-space coupling due to the limited design of reconfigurable antennas and the low optical tunability due to electrostatic pull-in of moving parts. In this paper, we propose efficient mid-infrared plasmonic nanoslits with variable nanometer-sized gaps giving rise to broad optical tunability. Our finite element method (FEM) analysis shows that by applying a voltage bias to asymmetric nanoslits supported on dielectric pillars, the gap width can be increased by more than 60 nm from an initial 1 nm. The large change in gap width results in a significant spectral shift in reflectance, while maintaining strong free-space coupling and a constant full width at half maximum (FWHM). We also analyze the effect of geometrical parameters on the nanometer-sized gap width and optical responses. Our nanoslits with simple geometry resulting in efficient optical coupling show promise for improving active metasurfaces and electromechanically tunable plasmonic devices.

On the plasmonic properties of a graphene nanoribbon and noble metal composite array

Graphene, composed of sp2 hybrid orbitals, is a hexagonal nanomaterial with a two-dimensional honeycomb lattice structure. Nowadays, thanks to its great electronic, optical, and thermal properties, there have been many promising applications based on graphene nanostructures. Under irradiations of external electromagnetic fields, the free electrons on graphene surfaces can be excited to oscillate collectively, resulting in highly localized surface plasmons. This phenomenon may provide foundations for designs of tunable plasmonic devices, therefore, graphene-based nanostructures have been widely studied so far. Besides, investigations on noble metals is another hot topic in the plasmonic community. With irradiations of incident lights, collective oscillations of free electrons on noble metals’ surfaces can also be induced, forming surface plasmons. The plasmonic characteristics can be adjusted by varying the parameters of the metals, including the geometries, thicknesses, as well as dimensions, etc. In this paper, a composite array consisting of graphene nanoribbons and noble metals is proposed, and its plasmonic properties are studied at mid-infrared wavelengths. In the structure, graphene nanoribbons are placed in between two SiO2 layers, and gold semi-cylinders and silver nanofilms are placed above the upper SiO2 layer, respectively. Using the finite difference time domain method, the light transmittance and electric field of the array are investigated, by varying the graphene’s Fermi energy and layer number, the noble metals’ sizes, as well as the period of the array, respectively. The results show that a plasmonic resonance feature is revealed in the 4–18 μm wavelength range, and the resonance characteristics can be tuned by adjusting the above parameters. The composite array structure proposed in this work may provide us with a new platform for the design of plasmonic devices in the mid-infrared regime.

Facilely Fabricated Zero-Bias Silicon-Based Plasmonic Photodetector in the Near-Infrared Region with a Schottky Barrier Properly Controlled by Nanoalloys.

Plasmonic Schottky devices have attracted considerable attention for use in practical applications based on photoelectric conversion, because they enable light to be harvested below the bandgap of semiconductors. In particular, silicon-based (Si) plasmonic Schottky devices have great potential for useful photodetection in the near-infrared region. However, the internal quantum efficiency (IQE) values of previously reported devices are low because the Schottky barrier is excessively high. Here, we are the first to develop AuAg nanoalloy-n-type Si plasmonic Schottky devices by cathodic arc plasma deposition. Interestingly, it is found that a novel nanostructure, which leads to the improvement of responsivities, is formed. Moreover, these plasmonic nanostructures can be fabricated in only ∼1 min. The fabricated AuAg nanoparticle-film structure enables proper control of the Schottky barrier height and increases the area of the Schottky interface for electron transfer. As a result, the considerably enhanced IQE of our device at a telecommunication wavelength of 1310 nm (1550 nm) without external bias is 4.6 (6.5) times higher than those in previous reports, and these responsivities are a record high. This approach can be applied to realize efficient photodetection in the NIR region and extend the use of light below the bandgap of semiconductors. This paves the way for future application advancements in a variety of fields, including photodetection, imaging, photovoltaics, and photochemistry.

Optical conductivity of a Bi2Se3 topological insulator with a THz transparent top gate

Abstract We have performed an investigation into the optical conductivity and magnetotransport properties of top-gated devices patterned on the topological insulator Bi2Se3 in order to determine the relative effects of the different carrier species that exist within these novel materials. We find that the topologically protected surfaces within our samples are partially screened from the action of the gate by trivial band-bending states formed at the top surface of the topological insulator. Despite this, the mobility of the topological surface carriers is significantly affected by the application of an external gate bias. Additionally, we find that the optical conductivity response is dominated by the topologically protected surface states, and that the optical conductivity is particularly sensitive to the scattering caused by the topological surfaces coupling to trivial states, arising from the bulk or band-bending induced surface states. These results will have interesting applications to the design of future plasmonic devices that incorporate topological materials.

Insight into plasmonics: resurrection of modern-day science (invited)

Plasmonics is a field of research and technology that focuses on the interaction between light and free electrons in a metal structure called plasmon. The study of plasmonics has gained significant attention in recent years due to its potential for several applications and its ability to manipulate light at nanoscale dimensions. Plasmonics enables the control of light at the nanoscale, far beyond the diffraction limit of conventional optics. This allows for the development of new devices and technologies with enhanced performance and functionality. In this paper, recent advances in plasmonics in medicine, agriculture, agriculture, environmental monitoring, lasers and solar energy harvesting are reviewed. Despite these promising prospects, plasmonic devices must overcome obstacles such as significant energy losses, complicated production processes, and the need for better material characteristics. Plasmonics will continue to advance because of ongoing work in nanotechnology, material science, and engineering, which will make it a more significant field with a wide range of usages in the future. In the end, the advantages and the limitations related to the realization of plasmonic devices in the real world are discussed.

Study of Bragg scattering in the presence of dipole-dipole interaction in plasmonic nanohybrids

We have developed a theory of the Bragg scattering for metallic nanohybrid made of an ensemble of metallic nanorods doped in a substrate. The substrate can gas, liquid or solid. An external laser field is applied to study the Bragg scattered light. The photons from the incident laser interact with the surface plasmons od nanorods and produce surface plasmon polaritons (SPPs). The incident laser field also induced dipoles in the ensemble of nanorods and they interact with each other via the dipole-dipole interaction (DDI). We have developed a theory for Bragg scattering for metallic nanohybrids using the coupled-mode formulism based on Maxwell’s equation in the presence of SPP and DDI fields. It is found that the theory of Bragg scattered depends on the susceptibility induced by the SPP and DDI fields. We used the quantum mechanical density matrix method to calculate the susceptibility. An analytical expression of the Bragg scattered light intensity is obtained. These expressions can be useful for experimental scientists and engineers who can used them to compare their experiments and make new types of plasmonic devices. Next, we have compared our theory with the experiment data for a nanohybrid made of ensemble of Au-nanoris doped in water. We found a good agreement between theory and experiments. We have also performed the numerical simulations to study the effect of SPP and DDI fields on the Bragg intensity. We have predicted an enhancement the Brag intensity due to the SPP and DDI couplings. The enhancement is due to the two extra scattering mechanisms of the SPP and DDI polaritons with acoustic phonons. We have also found that the one peak in the Bragg intensity can be split int many peaks due the SPP coupling, DDI coupling and phase factor. The splitting is due the Bragg factor appearing in the theory, and it includes the coupling of the incident laser, SPP and DDI electric fields with of acoustic phonons. The enhancement effect can be used to fabricate new types of nanosensors. Similarity, splitting phenomenon can be used to fabricate new types nanoswitches where one peak can be considered as the OFF position and many peaks can be considered as the ON position.

Investigation of a highly-sensitive aluminum-based plasmonic device using antimonene for sensing applications

Aluminum (Al) has gained popularity for surface plasmon resonance-based applications due to its affordability and compatibility with CMOS technology at the nanoscale. Over angle-interrogation mode, plasmonic interactions occurring at the metal-dielectric junction, are the outcomes of the attenuated total internal reflection phenomenon. Modified Al-based Kretschmann configuration results in phase-matching conditions that are seen as resonant points in the reflection characteristics. In our work, we have engineered an Al-based plasmonic device utilizing Antimonene as a 2D nanomaterial for bio-sensing purposes in the Near-Infrared (NIR) spectral domain. The study investigates the performance of Surface Plasmon Resonance (SPR) based refractive index sensor using different 2D nanomaterials with an optimized Al thickness of 30 nm. A comparative analysis of Al-based Kretschmann configurations in the presence of Graphene, Black Phosphorus, MXene, and Antimonene is presented using engineered intermediate layers. It is observed that the Al-antimonene-based plasmonic device exhibits improved sensing parameters in the NIR optical window.

Measuring dielectric and electro-optic responses of thin films using plasmonic devices.

This paper introduces a simple method for the measurement of the relative permittivity and the Pockels coefficient of electro-optic (EO) materials in a waveguide up to sub-THz frequencies. By miniaturizing the device and making use of plasmonics, the complexities of traditional methods are mitigated. This work elaborates the fabrication tolerance and simplicity of the method, and highlights its applicability to various materials, substrates and configurations. The method is showcased using drop-casted perovskite barium titanate (BaTiO3, BTO) nano-particle thin-films and it has previously been used to measure epitaxial thin film BTO. In this work we show the effective relative permittivity of drop casted BTO to be εeff ∼ 30 at 200 MHz, dropping to ∼ 18 at 67 GHz and similarly, the effective Pockels coefficient was found to be reff ∼ 16 at 350 MHz and ∼ 8 at 70 GHz. These values are a factor > 50 below the values found for thin film BTO. Yet, the fact that the method can be applied to such different samples and Pockels strengths gives testimony to its versatility and sensitivity.

Elliptical vibration chiseling: a novel process for texturing ultra-high-aspect-ratio microstructures on the metallic surface

Highlights Elliptical vibration chiseling is proposed based on a game-changing process principle for the high-efficient texturing of ultrahigh-aspect-ratio surface microstructures. Uniformed microstructures with an aspect ratio of 2–12 in the spacing scale of 1–10 μm have been successfully fabricated using elliptical vibration chiseling. The developed process model of elliptical vibration chiseling has been verified by the measured results of the microstructures’ geometric parameters. An inclined elliptical trajectory of tool vibration is more suitable for elliptical vibration chiseling than the standard elliptical trajectory. The deterministic process effects on the surface generation of microstructure in elliptical vibration chiseling have been demonstrated.

Isotropic optical response and edge plasmons in MoS[formula omitted] monolayer induced by oxygen absorption

Defects play a crucial role in altering the electronic and optical characteristics of two-dimensional (2D) semiconductors, which is highly significant for the advancement of next-generation electronic and optoelectronic devices. In this study, we employ first-principles density functional theory (DFT) and time-dependent DFT calculations to explore the impact of oxygen defects on the electronic, optical, and plasmonic properties of monolayer MoS2. Our calculations reveal that the presence of an oxygen defect in the absorption position of the MoS2 monolayer leads to a predominant photoabsorption in the visible region of the electromagnetic spectrum, as well as an isotropic optical response and the emergence of edge plasmons. Conversely, when an oxygen defect is located in the adsorption position of the MoS2 monolayer, it generates deep midgap states within the bandgap, resulting in an anisotropic optical response and the partial decay of edge plasmons. By obtaining a comprehensive understanding of the effects of defects on photoabsorption and plasmonics, our study provides valuable insights for enhancing the performance of optical and plasmonic devices based on 2D materials.

Excitation of Multiple Fano Resonances in a Plasmonic Device and Carcinoma Detection

Excitation of Multiple Fano Resonances in a Plasmonic Device and Carcinoma Detection

Tailoring linear and nonlinear plasmons of metal/MoS2/metal nanostructures.

We investigated the linear and nonlinear response of the localized surface plasmons (LSPs) and surface plasmon polaritons (SPPs) in metal and MoS2 nanostructures. The results show that the response of LSPs and SPPs has an important influence on the energy exchange. SPPs with unique non-radiative characteristics can be used as energy recovery tanks to reuse the radiated energy of LSPs and promote the production of hot carriers. The energy exchange through plasmon modes can promote the transfer of hot electrons in the Au grating, the MoS2 layer, and the metal film. The fundamental field induces the increase of the second harmonic wave by introducing the second-order nonlinear source. In addition, the evolution of the lifetime of linear and nonlinear plasmonic modes is also investigated to study the underlying mechanism of the micro process in the plasmonic-photonic interaction. The plasmonic energy exchanging configuration overcomes the challenge by utilizing hot carriers. It is instructive in terms of improving the linear and nonlinear performance of plasmonic opto-electronic devices.

Bonding states of gold/silver plasmonic nanostructures and sulfur-containing active biological ingredients in biomedical applications: a review.

As one of the most instrumental components in the architecture of advanced nanomedicines, plasmonic nanostructures (mainly gold and silver nanomaterials) have been paid a lot of attention. This type of nanomaterial can absorb light photons with a specific wavelength and generate heat or excited electrons through surface resonance, which is a unique physical property. In innovative biomaterials, a significant number of theranostic (therapeutic and diagnostic) materials are produced through the conjugation of thiol-containing ingredients with gold and silver nanoparticles (Au and Ag NPs). Hence, it is essential to investigate Au/Ag-S interfaces precisely and determine the exact bonding states in the active nanobiomaterials. This study intends to provide useful insights into the interactions between Au/Ag NPs and thiol groups that exist in the structure of biomaterials. In this regard, the modeling of Au/Ag-S bonding in active biological ingredients is precisely reviewed. Then, the physiological stability of Au/Ag-based plasmonic nanobioconjugates in real physiological environments (pharmacokinetics) is discussed. Recent experimental validation and achievements of plasmonic theranostics and radiolabelled nanomaterials based on Au/Ag-S conjugation are also profoundly reviewed. This study will also help researchers working on biosensors in which plasmonic devices deal with the thiol-containing biomaterials (e.g., antibodies) inside blood serum and living cells.

Active control of plasmon coupling via simple electrochemical surface oxidation/reduction of Au nanoparticle agglomerates.

Reversible tuning of plasmon coupling of Au nanoparticle (AuNP) agglomerates containing dimers as the main component was achieved via electrochemical surface oxidation/reduction of the AuNP surface. The system required no reactant except for water and was almost finished within a unit second, which leads to novel active plasmonic devices.