Plasmonic Arrays Research Articles

Numerical investigation on the polarization-dependent light extraction of 275-nm AlGaN based nanowire with bowtie antenna array or passivation layer

Abstract The low light extraction efficiency (LEE) is one of the major factors hindering the application of AlGaN based deep ultraviolet (DUV) light-emitting diodes (LEDs). Here we investigate the LEE of AlGaN based nanowire (NW) DUV LEDs emitting at 275 nm for bare NW, NW integrated with aluminum (Al) bowtie antenna array, and NW with passivation layer under transverse-electric (TE) and transverse-magnetic (TM) polarization. It is observed that by integrating plasmonic Al bowtie antenna array with AlGaN based NW, the LEE up to 83% and 74% can be achieved under TE and TM polarization. In addition, the effect of the three different passivation layer SiO2, SiNx and AlN on the LEE of AlGaN based NW is also analysed, the results suggests that SiO2, which has smaller refractive index than NW core, could extract more photons from the NW and lead to large enhancement of LEE. For SiNx and AlN passivation layer, which has refractive index similar to the NW core, have strong coupling with the NW core, when the thickness of passivation layer satisfy resonance coupling conditions, the LEE could be achieved more than 80% for both TE and TM polarization. These integrated NW/antenna array and NW with passivation layer system can provide guidelines for designing other nano-photonic devices.

Design of a square-horn hybrid plasmonic nano-antenna array using a flat lens for optical wireless applications with beam-steering capabilities

This paper introduces a Hybrid Plasmonic Nano-Antenna (HPNA) with a gradient-index dielectric flat lens modeled with different materials to enhance and steer the radiation in a particular direction based on a phase shift array. Firstly, the design of hybrid plasmonic Nano-Antenna (NA) is introduced and analyzed considering different horn-shapes such as diamond, hexagonal, circular, rectangular, and square shapes. The commercial software Computer Simulation Technology-Microwave Studio (CST-MWS) is used to analyze the radiation characteristics of the plasmonic NAs at the standard telecommunication wavelength of 1,550 nm. The produced horn-shaped nano-antenna made up from gold cladding with low- and high-index dielectric materials of SiO2 and InGaAs, respectively. The gain of the Square Horn shape Hybrid Plasmonic Nano-Antenna (SHHPNA) achieves the greatest gain with a value of 10.7 dBi at the desired frequency and the return loss reached -18.09 dB due to the wide aperture area for SHHPNA, which results in a narrower beam-width and higher gain. Moreover, by using two different shapes of dielectric flat lens to enhance the antenna’s performance by improving directivity while correspondingly reducing beam-width, the gain is enhanced and reaches 16.7 for SHHPNA with a circular lens and 16.9 for SHHPNA with a rectangular lens compared with the traditional NA that equal to 9.03 dBi. The main lobe for SHHPNA with each lens is more directed, with Side Lobe Level (SLL) and Half Power Beam-Width (HPBW) of -13.1 dB and 16.5° for SHHPNA with a circular lens and -15.1 dB and 15.4° for SHHPNA with a rectangular lens, respectively. In addition, the array configuration was investigated, and the gain was found to be 21 dBi for the single row array of 4×1 and 23.2 dB for the array of 3×3. Moreover, the array of 4×1 and 3×3 with +90° showed gains of 18.6 dBi and 20.7 dBi, respectively, compared to traditional paper with gains of 11.20 dBi and 13.1 dBi.

Exploration ofcucurbituril-mediated SERS plasmonic nanoarrays with sub-nanometer gaps.

The uneven distribution of hotspots and the challenges associated with precise analyte localization within these hotspots present significant hurdles in the field of surface-enhanced Raman scattering (SERS). Here, at the water-oil interface, gold nanoparticles (AuNPs) interconnected by cucurbiturils[8] (CB[8]) with sub-nanometer gaps (AuNPs:CB[8]) were organized into plasmonic arrays. This arrangement was engineered to generate highly efficient hotspots. The CB[8] molecules, serving a dual role, not only facilitated the assembly of AuNPs with sub-nanometer (~ 1nm) gaps to create intense plasmonic hotspots but also acted as molecular traps, enabling the precise localization of molecules within these hotspots. By comparing the enhancement effect of probe molecule on Au nanofilm, AuNPs:CB[8] colloids, and AuNPs:CB[8] nanofilm, it was found that the SERS intensity of the E1 characteristic peak in AuNPs:CB[8] nanofilm is five times higher than that on Au nanofilm, and more than 104 times higher than that of AuNPs:CB[8] colloids. The gaps are also accessible to different electronegativite molecules, such as estrone, p-aminoazobenzene, or methylene blue, which are captured at the plasmonic hotspots by the interaction of CB[8]. Themethod was employed for the practical detection of artificial antioxidant butylated hydroxyanisole (BHA), which has a weak Raman scattering cross-section, by coupling it with a reaction to enhance its SERS effect. The detection limit of BHA in soybean oil sample is 5.89 × 10-8mol/L, with the recovery range 85.1-115%. In conclusion, this hot-spot design and molecular capture approach will offer a highly effective method for detecting weak Raman scattering cross-section molecules and holds great promise for practical applications in the future.

Plasmonic antennas based on rectangular graphene nanoribbons with controlled polarization of terahertz and infrared radiation

Background. To develop new terahertz wireless communication systems with high throughput and transmission speeds, such as 6G and above, effective control of the polarization direction of emitted terahertz waves is necessary, but most methods are technologically complex and expensive. The implementation of terahertz antennas and devices based on 2D materials such as graphene solves the problem associated with developing effective control. Aim. Study of the possibility of controlling the polarization of terahertz and IR radiation of plasmonic antennas based on rectangular graphene nanoribbons by changing the chemical potential (application of an external electric field). Methods. This important scientific problem related to the design of terahertz antennas can largely be solved by simulation using the electrodynamic simulation program CST MWS 2023. Results. Plasmon terahertz antennas based on rectangular graphene nanoribbons were chosen as the object of analysis and the possibility of emitting waves of two orthogonal polarizations was shown. Methods have been identified for controlling the polarization of terahertz and IR radiation from such antennas, based on the selection of operating frequencies corresponding to the resonances of the modes of surface plasmon-polaritons, and the application of metallization to the dielectric substrate. Conclusion. The ability to control the polarization of terahertz and IR radiation makes it possible to create both new elements of plasmonic antenna arrays and new communication technologies, including future 6G networks.

Enhancing photovoltaic performance of organic solar cells by embedding plasmonic Ag nanocuboid array in the active layer

Enhancing photovoltaic performance of organic solar cells by embedding plasmonic Ag nanocuboid array in the active layer

Titanium Nitride as an Alternative Plasmonic Material for Plasmonic Enhancement in Organic Photovoltaics

This paper investigates TiN for its potential to enhance light-harvesting efficiency as an alternative material to Au for nanoscale plasmonic light trapping in thin-film solar cells. Using nanosphere lithography (NSL), plasmonic arrays of both Au and TiN are fabricated and characterized. Later, the fabricated TiN and Au arrays are integrated into a thin-film organic photovoltaic (OPV) device with a PBDB-T:ITIC-M bulk heterojunction (BHJ) active layer. A comparative study between these Au and TiN nanostructured arrays evaluates their fabrication process and plasmonic response, highlighting the advantages and disadvantages of TiN compared to a conventional plasmonic material such as Au. The effect of the fabricated arrays when integrated into an OPV is presented and compared to understand the viability of TiN. As one of the first experimental studies utilizing TiN arrays for the plasmonic enhancement of photovoltaics, the results offer valuable insight that can guide future applications and decisions in design.

A Plasmonic Nanoledge Array Sensor for Selective Detection of Cardiovascular Disease Biomarkers in Human Whole Blood.

Optical sensors face challenges when detecting ultralow amounts of analytes in whole blood, including signal quenching due to optical absorption and false positives due to nonspecific binding. This study introduces gold nanoscale array features termed nanoledges (NLs), which interact with incident white light to produce a transmitted surface plasmon resonance (tSPR) signal. This extraordinary optical transmission (EOT) spectrum occurs in the near-infrared (NIR) region, thereby minimizing signal quenching caused by visible-light absorption from blood proteins and pigments. To develop a sensitive, selective, and label-free optical biosensor for detecting various levels of cardiac troponin I (cTnI) in very small volumes of whole blood samples, DNA aptamers are tethered to the NL surface, specifically binding to the cTnI biomarker. This biological binding activity alters the refractive index at the NL surface, causing a peak shift in the EOT spectrum and enabling quantification of cTnI levels. The NL array chip demonstrated high sensitivity for cTnI detection in buffer, human serum (HS), and human whole blood (HB), with detection limits of 0.079, 0.084, and 0.097 ng/mL, respectively. Control measurements using blank target mediums and those containing up to 125 ng/mL of other proteins, such as myoglobin, creatine kinase, and heparin, showed minimal interference and high specificity. The NL plasmonic array's performance in biosensing underscores its promise for clinical analysis and its potential development as a point-of-care platform for early cardiovascular disease (CVD) diagnostics.

Integration of highly ordered plasmonic nanocavity array structure with the electrostatic driving force for dynamic control of SERS signals and label-free detection of λ-DNA

Integration of highly ordered plasmonic nanocavity array structure with the electrostatic driving force for dynamic control of SERS signals and label-free detection of λ-DNA

Self-Driven Graphene Photodetector Arrays Enabled by Plasmon-Induced Asymmetric Electric Field.

Gap surface plasmon (GSP) modes enhance graphene photodetectors (GPDs)' performance by confining the incident light within nanogaps, giving rise to strong light absorption. Here, we propose an asymmetric plasmonic nanostructure array on planar graphene comprising stripe- and triangle-shaped sharp tip arrays. Upon light excitation, the noncentrosymmetric metallic nanostructures show strong light-matter interactions with localized field close to the surface of tips, causing an asymmetric electric field. These features can accelerate the hot electron generation in graphene, forming a directional diffusion current. Accordingly, the artificial GPDs exhibit a wavelength-dependence behavior covering the wavelength range from 0.8 to 1.6 μm, with three photoresponse maxima corresponding to the nanostructures' resonances. Additionally, the polarization-dependent GPDs can realize a responsivity of ∼25 mA/W and a noise equivalent power of ∼0.44 nW/Hz1/2 at zero bias when excited at the resonance of 1.4 μm. Overall, our study offers a new strategy for preparing compact and multifrequency infrared GPDs.

Flexible plasmonic microneedle array-based SERS sensor for pH monitoring of skin interstitial fluid

Interstitial fluid (ISF) is a prevalent accessible and information-rich biofluid, and monitoring pH level of interstitial fluid plays a crucial role in the physiological health assessment. However, facile extraction of ISF and sensitive detection of pH is still a great challenge. Herein, a flexible plasmonic microneedle array (PMNA)-based SERS sensor was developed for facile and sensitive pH monitoring of skin ISF. The flexible microneedle arrays were fabricated by norland optical adhesive 65 (NOA65), and coated with pH-sensitive 4-Mercaptobenzoic acid (4-MBA)-labeled silver nanoparticles (Ag NPs) by electrostatic assembly. The proposed flexible PMNA-based SERS sensor has a good linear response in the pH range of 5 to 9 which covers the normal pH level in skin interstitial fluid. The ISF extracted from porcine skin was chosen as the test model, and the pH levels detected by the PMNA-based SERS sensors were well consistent with the theoretical results. Besides, the proposed flexible SERS sensors show good mechanical robustness, sensing stability, and biocompatibility before and after skin insertion, which can be a potential analytical tool for practical detection of pH levels in ISF and provide technical support for SERS-based wearable biosensing.

4 × 4 graphene nano-antenna array for plasmonic sensing applications

The manuscript presents the design and investigation of square and L-shaped graphene plasmonic nano-antenna arrays on a silicon dioxide substrate for plasmonic biosensing applications. The design parameters, such as the shape of the nanostructure, spacing between the antenna array elements, size of the antenna array and chemical potential of the graphene are used to analyze the plasmonic resonance characteristics of the proposed plasmonic nano-antenna array. Initially, dispersive characteristics of graphene, such as conductivity, permittivity and refractive index are analyzed using its chemical potential for the validation of the graphene material for plasmonic sensing applications. The proposed square and L-shaped nanopatch antenna structures are radiating at 30 THz with a reflection coefficient of -28.4 dB and − 44.6 dB respectively at 0.1 eV chemical potential. It is observed that graphene nanopatch antenna radiates at 30 THz, 115 THz and 176 THz at a chemical potential of 1.3 eV. Further, the study demonstrated that the designed square and L-shaped nano-antenna exhibit a gain of 3.52 dB and 9.51 dB respectively at 30 THz. The gain can be increased further using a square and L-shaped nano-antenna array of dimensions 2 × 2, 3 × 3 and 4 × 4. It is observed that maximum gains of 33.44 dB and 30.86 dB are obtained for the square and L-shaped 4 × 4 plasmonic nanoarray antenna respectively. Finally, a nanocircuit model of square and L-shaped nano-antennas is proposed and validated through CST simulations.

Label-Free Detection of DNA Base Mutation and Hybridized DNA by an Electrostatically Modified 3D Plasmonic Array.

Surface-enhanced Raman scattering (SERS) represents a promising avenue for DNA detection as it offers intrinsic chemical insights with high sensitivity compared to conventional methods. However, label-free and quantitative detection of unmodified DNA by SERS remains a major challenge in DNA analysis. To overcome this challenge, we propose a positively charged plasmonic nanosurface for DNA capture and quantitative analysis. Highly sensitive and uniform SERS enhancement was realized by a three-dimensional plasmonic array supporting well-designed hybrid plasmonic modes. Subsequently, the plasmonic array was modified with an electrostatically functionalized PDDA (poly(diene-dimethylammonium-chloride)) self-assembled monolayer in a single step. The effectiveness of the resulting PDDA-SERS substrate was demonstrated by the label-free and quantitative detection of base content and base mutation in hybridized DNA. The PDDA-SERS substrate provides a robust platform for SERS analysis not only of DNA but also of other electronegative analytes.

Plasmonic array at liquid-liquid interface for trace microplastics detection

Microplastics (MPs) pollution has become a focal point of global concern, as the widespread distribution of MPs in the environment poses a potential threat to ecosystems and human health. Despite surface-enhanced Raman scattering (SERS) being one of the most promising detection techniques, the “coffee ring effect” of MPs and their unique size scale make effective contact with SERS substrates challenging. Here, we propose a novel strategy for MPs detection by constructing a plasmonic metasurface at the liquid-liquid interface (LLI). The fluidic properties of LLI provide more flexibility for the uniform dispersion of MPs and the assembly of plasmonic arrays. MPs are captured and assembled on an atomic-level metasurface in a core-shell structure (AuNPs@MPs), providing abundant “hot spots” and additional volume-enhanced Raman effects. This results in enhanced electromagnetic field around MPs and increased enhancement factors, demonstrating high SERS sensitivity and uniformity. This sensing platform provides a new approach for trace detection of MPs and has been validated in practical matrix.

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.

Unveiling the Influence of Line Shape of Surface Plasmon Resonances on Exciton–Plasmon Strong Coupling

AbstractStrong coupling between surface plasmon resonance (SPR) modes and excitons holds great potential for many chemical and physical applications. However, a clear understanding on how far‐field spectral characteristics of SPR (linewidths and intensity) affect the coupling strength remains unclear because these parameters are difficult to be individually tuned. These spectral characteristics are associated with the damping rate and field enhancement that depend on the morphology of the plasmonic nanostructure. In this work, the influence of the SPR line shape on exciton‐plasmon coupling is systematically investigated by delicately tuning the linewidths and resonance intensities of the plasmonic arrays. It is found that the SPR modes with narrow linewidths or large intensity are favorable for the exciton–plasmon system to achieve strong coupling. The obtained clear relationships between the SPR line shape and coupling strength provide guidance for the design and optimization of exciton‐plasmon coupling systems, favoring the highly efficient manipulation of exciton polaritons and enabling specific applications driven by strong coupling.

Manipulating the topological phase of coupled modes in a plasmonic array via engineering near-field asymmetry: From zigzag arrangement to dielectric substrate

Manipulating the topological phase of coupled modes in a plasmonic array via engineering near-field asymmetry: From zigzag arrangement to dielectric substrate

Rotational Evolution Characteristic and High Figure of Merit Sensing of Plasmonic Nano-Crescent Array

Rotational Evolution Characteristic and High Figure of Merit Sensing of Plasmonic Nano-Crescent Array

Demonstration of extrinsic chirality in self-assembled asymmetric plasmonic metasurfaces and nanohole arrays

Chirality, the lack of mirror symmetry, can be mimicked in nanophotonics and plasmonics by breaking the symmetry in light-nanostructure interaction. Here we report on versatile use of nanosphere lithography for the fabrication of low-cost metasurfaces, which exhibit broadband handedness- and angle-dependent extinction in the near-infrared range, thus offering extrinsic chiro-optical behavior. We measure wavelength and angle dependence of the extinction for four samples. Two samples are made of polystyrene nanospheres asymmetrically covered by silver and gold in one case and silver only in the other case, with a nanohole array at the bottom. The other two samples are nanohole arrays, obtained after the nanosphere removal from the first two samples. Rich extrinsic chiral features are governed by different chiro-optical mechanisms in the three-dimensional plasmonic semi-shells and planar nanohole arrays. We also measure Stokes parameters in the same wavelength and incidence angle range and show that the transmitted fields follow the extrinsic chirality features of the extinction dissymmetry. We further study the influences of the nanostructured shapes and in-plane orientations on the intrinsic vs extrinsic chirality. The nanoholes are modelled as oval shapes in metal, showing good agreement with the experiments. We thus confirm that nanosphere lithography can provide different geometries for chiral light manipulation at the nanoscale, with the possibility to extend functionalities with optimized oval shapes and combination of constituent metals.

Design of near-perfect absorptance in few-layer WSe2 via cooperative enhancement mechanisms

Two-dimensional transition metal dichalcogenides are of growing interest for flexible optoelectronics and power applications, due to their tunable optical properties, lightweight nature, and mechanical pliability. However, their thin nature inherently limits their optical absorption and, therefore, efficiency. Here, we propose a few-layer WSe2 optoelectronic device that achieves near perfect absorption through a combination of optical effects. The WSe2 can be scalably grown below an Al2O3 superstrate. Our device includes a corrugated back reflector, modeled as a plasmonic nanowire array. We investigate the entire range of widths of the corrugations in the back reflector, including the edge cases of a simple back mirror (width equal to period) and a Fabry-Perot cavity (zero width). We demonstrate the zero-mode enhancement arising from the back reflector, the weakly coupled enhancement arising from the Fabry-Perot cavity, and the strongly coupled enhancement arising from the localized surface plasmon resonance of the nanowires, explain the physical nature of the spectral peaks, and theoretically model the hybridization of these phenomena using a coupled oscillator model. Our champion device exhibits 82% peak absorptance in the WSe2 alone, 92% in the WSe2 plus nanowires, and 98% total absorptance. Thus, we achieve a near-perfect absorber in which most of the absorption is in the few-layer WSe2, with a desirable device framework for integration with scalable growth of the WSe2, thereby making our designs applicable to a range of practical optoelectronic devices.

Ultra-thin size-controllable surface plasmon polariton laser by PDMS-assisted imprinting

Plasmonic laser has great potential to overcome the optical diffraction limit, playing a crucial role in advancing nanophotonics and nanoelectronics for on-chip integration. However, current plasmonic lasers face several challenges, such as the difficulty in controlling nanowire (NW) size, disordered arrangement, and complicated fabrication process. Herein, ultra-thin gain media for plasmonic lasers below the cutoff size of the photonic mode are prepared using the polydimethylsiloxane-assisted imprinting. This method enables precise control over the size of the perovskite NW, with the minimum size achievable being 60 nm. As a result, the plasmonic lasing is achieved from the CsPbBr3 NW-based device with a threshold as low as ∼49.13 μJ cm−2 and a Quality Factor (Q) of 1803 at room temperature, demonstrating its capability for achieving high-quality lasing. Meanwhile, a dual-pumping time-resolved fluorescence study suggests that the radiative recombination lifetime of CsPbBr3 NWs is shortened by a factor of 10 due to the Purcell effect, confirming the plasmonic effect exhibited by the device. Furthermore, a plasmonic laser array is developed using this method, demonstrating the applicability of the imprinting method in complex graphic fabrication. This breakthrough provides a solution for the application of plasmonic laser arrays in optoelectronic integration.