Plasmon Hybridization Research Articles

Efficient manipulation of plasmonic modes in single symmetry-breaking Ag nanocube

Efficiently manipulating plasmonic modes by adjusting geometry, spatial arrangement, and the nature of the material has shown great potential in wide applications including ultrasensitive sensing, optical modulation, and surface-enhanced spectroscopy. Symmetry breaking as an effective geometry-controlled method can induce plasmonic hybridization and further tune resonant wavelength, strength, and electromagnetic fields. Herein, through introducing cavity along the cubic lateral edges, we theoretically design symmetry-breaking Ag nanocube that is capable of arbitrarily tuning plasmonic modes based on plasmon hybridization theory. Originated from the hybridization of the nanocube and cavity, bonding and anti-bonding dipole–dipole coupled modes simultaneously exhibit trends of blueshifts and redshifts by decreasing the overlapped domain and by increasing the radius of cavity. Moreover, the hybrid modes can be independently tuned by changing the edge length of the cube and the number and the location of cavity. These findings not only advance the understanding of the mechanism of light-matter interactions in symmetry-breaking Ag nanocube but also provide further guidance for designing efficient nanophotonic platforms in plasmon-enhanced spectroscopy and optical wave manipulations.

Second harmonic generation from grating-coupled hybrid plasmon–phonon polaritons

Polaritons can provide strong optical field enhancement allowing them to boost light–matter interaction. Here, we experimentally observe enhancement in mid-infrared second-harmonic generation (SHG) using grating-coupled surface phonon polaritons of the 6H-SiC surface. In our experiment, we measure the SHG along the polariton dispersion by changing the incidence angle of the excitation beam. We observe hybridization between the propagating surface phonon polaritons and localized plasmon resonances in the gold grating, evidenced by the modification of the polariton dispersion as we change the area ratio of grating and substrate. Design options for engineering the plasmon–phonon polariton hybridization are discussed. Overall, we find a rather low yield of polariton-enhanced SHG in this geometry compared to prism-coupling and nanostructures and discuss possible origins.

Investigation on the AgPt and AgPd hybrid alloy nanoparticles (HANPs) for the hybrid MoS2/ZnO/HANP UV photodetector application

Hybrid photodetectors made of two or more nanomaterial components can offer the high potential for advanced photodetection applications with enhanced light absorption, improved efficiency and structural tunability. A hybrid UV photodetector (PD) configuration incorporating the plasmonic hybrid alloy nanoparticles (HANP), ZnO quantum dots (QDs) and MoS2 nanoflakes, namely MoS2/ZnO/HANP PD, is demonstrated. The optimized MoS2/ZnO/HANP PD exhibits a high photocurrent of 5.66 mA at 0.34 mW/mm2 under 385 nm illumination with two orders of improvement from the bare ZnO, which is one of the highest photocurrents by the ZnO-based PDs. It also demonstrates high figure-of-merits with the responsivity of 14,523 mA/W, detectivity of 8.13 × 1011 jones, and external quantum efficiency (EQE) of 4,680 %, outperforming most of the ZnO-based hybrid architectures. The enhanced photoresponse is primarily attributed to the significantly enhanced hot electron generation by the AgPd HANPs and photocarrier collection through the ZnO QD layer. MoS2 nanoflakes also provide additional photon absorption sites and boost the photo-carrier transfer process. HANPs are grown by adapting a dual-step solid-state dewetting process (SSD) approach and the superiority of AgPd HANPs is confirmed by systematic investigation, FDTD simulation and comparison of AgPt and AgPd HANPs.

Multiscale Plasmonic Refractory Nanocomposites for High-Temperature Solar Photothermal Conversion.

Development of a refractory selective solar absorber (RSSA) is the key to unlock high-temperature solar thermal and thermochemical conversion. The fundamental challenge of RSSA is the lack of design and fabrication guidelines to simultaneously achieve omnidirectional, broadband solar absorption and sharp spectral selectivity at the desired cutoff wavelength. Here, we realize a ruthenium-carbon nanotube (Ru-CNT) nanocomposite RSSA with multiscale nanoparticle-on-nanocavity plasmonic modes. Ru conformally coated on the sidewalls of CNTs enables a spoof surface plasmon polariton mode for spectra selectivity; Ru nanoparticles formed at the tips of CNTs enable a localized surface plasmon resonance mode and plasmon hybridization for omnidirectional broadband solar absorption. The fabricated Ru-CNT RSSA has a total solar absorption (TSA) of 96.1% with sharp spectral cutoff at 2.21 μm. The TSA is maintained at over 90% for an incident angle of 56°. Our findings therefore guide full-spectrum optical and thermal control from visible to the far-infrared.

Ultrafast Laser-Induced Formation of Hollow Gold Nanorods and Their Optical Properties.

Laser irradiation has been shown to be an efficient means to modify structures and shapes of plasmonic nanoparticles for tuning their properties. Thermomechanical deformations of single-crystal and penta-twinned gold nanorods by femtosecond laser irradiations have been studied by classical molecular dynamics simulations. It is demonstrated that hollow gold nanorods could be formed by femtosecond laser irradiations under certain conditions of maximum temperatures in nanorods by laser heating and cooling rates due to the extrinsic solvent. For a given maximum temperature and cooling rate, a larger cavity is induced in the irradiated single-crystal nanorod. The results also indicate that at the same cooling rate a higher threshold of maximum temperature can be required for producing the cavity in the twinned nanorod. The optical spectra of the laser-irradiated gold nanorods are calculated, and the shifts in the surface plasmon resonance peak of the nanorods are illustrated due to the thermal reshaping and the plasmon hybridization mechanism. Moreover, we show the formation of the hollow gold nanorod possessing the surface plasmon resonance peak in the second near-infrared window and a relatively small aspect ratio (∼2.8), which is highly desirable and suitable for serving as agents in biomedical imaging and photothermal therapy applications.

Highly Directive Graphene Based Hybrid Plasmonic Nanoantenna for Terahertz Applications

To satisfy the necessity for elevated data transmission rates in 5G and beyond networks, terahertz band communication (0.1 - 10 THz) is envisaged as a crucial wireless technology. Two-dimensional graphene nanomaterial is being extensively integrated into the plasmonic antennas as it allows them to resonate in the terahertz wave spectrum. In this paper, a graphene-based hybrid terahertz plasmonic nano-scale antenna has been modelled to acquire a maximum gain and directivity of 8.1 dB and 8.23 dBi, respectively, by varying the conductivity of graphene via gate bias voltage. Moreover, a combination of several tailored radiating layers of silver, SiO2 and graphene sheets is arranged in the proposed nanoantenna in such a way that the return loss (S11) of -26.595 dB and a wider bandwidth of 1241.3 GHz are obtained. It is evident that the proposed graphene-based hybrid plasmonic nanoantenna could be considered as an ideal candidate for terahertz communication owing to its excellent radiation characteristics.

Double Fano Resonance and Independent Regulation Characteristics in a Rectangular-like Nanotetramer Metasurface Structure.

Fano resonance, which is based on a plasmonic metasurface, has many potential applications in various fields, such as biochemical sensors, slow light effect, and integrated optical circuits. In this study, a rectangular-like nanotetramer metasurface structure composed of four round-head nanorods was designed. The transmission spectrum, surface charge, and electrical field distributions of the proposed structure were simulated using the finite element method. A double Fano resonance profile was observed in the transmission spectrum. One of the Fano resonances was caused by the symmetry breaking and plasmon hybridization between the horizontal double rods, whereas the other resonance was due to the plasmonic modes’ hybridization among four nanorods. These resonances could be independently tuned because of different formation mechanisms. The number of Fano resonances could be adjusted by changing the coupling distance between the horizontal and vertical rods. The results contributed to designing the highly sensitive sensors based on the plasmonic metasurface.

Electrically controlled molecular fingerprint retrieval with van der Waals metasurface

Polaritons in two-dimensional van der Waals (vdW) materials possess extreme light confinement, which have emerged as a potential platform for next-generation biosensing and infrared spectroscopy. Here, we propose an ultra-thin and electric tunable graphene/hexagonal boron nitride/graphene metasurface for detecting molecular fingerprints over a broad spectrum. The vdW metasurface supports hybrid plasmon–phonon polariton resonance with high-quality factor (Q > 120) and electrically controlled broadband spectra tunability from 6.5 to 7 μm. After coating a thin layer of bio-molecular (e.g., CBP) on top of the metasurface, the molecular absorption signatures can be readout at multiple spectral points and, thus, achieve broadband fingerprint retrieval of bio-molecules. Additionally, our electric tunable metasurface works as an integrated graphene-based field-effect transistor device, without the need of multiple resonance generators such as angle-resolved or pixelated dielectric metasurfaces for broadband spectra scanning, thereby paving the way for highly sensitive, miniaturized, and electrically addressed biosensing and infrared spectroscopy.

Hybrid plasmonic–dielectric metal-nanowire coupler for high-efficiency broadband nonlinear frequency conversion

Pursuing nanometer-scale nonlinear converters based on second harmonic generation (SHG) is a stimulating strategy for bio-sensing, on-chip optical circuits, and quantum information processing, but the light-conversion efficiency is still poor in such ultra-small dimensional nanostructures. Herein, we demonstrate a highly enhanced broadband frequency converter through a hybrid plasmonic–dielectric coupler, a ZnTe/ZnO single core–shell nanowire (NW) integrated with silver (Ag) nanoparticles (NPs). The NW dimension has been optimized to allow the engineering of dielectric resonances at both fundamental wave and second harmonic frequencies. Meanwhile, the localized surface plasmon resonances are excited in the regime between the Ag NPs and ZnTe/ZnO dielectric NW, as evidenced by plasmon-enhanced Raman scattering and resonant absorption. These two contributors remarkably enhance local fields and consequently support the strong broadband SHG outputs in this hybrid nanostructure by releasing stringent phase-matching conditions. The proposed nanoscale nonlinear optical converter enables the manipulation of nonlinear light–matter interactions toward the development of on-chip nanophotonic systems.

Sericin-Based Bio-Inspired Nano-Engineering of Heterometallic AgAu Nanocubes for Attomolar Mefenamic Acid Sensing in the Mobile Phone-Based Surface Plasmon-Coupled Interface

Engineering photo-plasmonic platforms with heterometallic nanohybrids are of paramount significance for realizing augmented sensitivity in fluorescence-based analytical detection. Although myriad nanomaterials with versatile functionalities have been explored in this regard in the surface plasmon-coupled emission (SPCE) interface, light harvesting using nano-antennas synthesized via sustainable bio-inspired routes still remains a high priority in current research. Our study provides a rational design for in situ fabrication of nanoparticles of silver, gold, and their plasmonic hybrids using biocompatible, non-hazardous sericin protein (obtained Bombyx mori) as the reducing and capping agent. The one-pot, user-eco-friendly technology demonstrated here utilizes UV irradiation to promote the photo-induced electron transfer mechanism, thereby yielding nanomaterials of tunable optoelectronic functionalities. The resulting homometallic and heterometallic nanohybrids with robust localized surface plasmon resonances (LSPR) showed strong light-confining attributes when interfaced with the propagating surface plasmon polaritons (SPPs) of the SPCE platform, thereby yielding tunable, highly directional, polarized, and amplified fluorescence emission. The experimentally obtained emission profiles displayed an excellent correlation with the theoretically obtained dispersion diagrams validating the spectro-plasmonic results. The abundant hotspots from AgAu nanocubes presented in excess of 1300-fold dequenched fluorescence enhancement and were utilized for cost-effective and real-time mobile phone-based sensing of biologically relevant mefenamic acid at an attomolar limit of detection. We believe that this superior biosensing performance accomplished using the frugal bioinspired nano-engineering at hybrid interfaces would open new doors for developing nanofabrication protocols with the quintessential awareness of the principles of green nanotechnology, consequently eliminating hazardous chemicals and solvents in the development of point-of-care diagnostic tools.

Low Loss Hybrid Plasmonic Waveguide with Variable Nonlinearity and Ultralow Dispersion

Low Loss Hybrid Plasmonic Waveguide with Variable Nonlinearity and Ultralow Dispersion

An image interaction approach to quantum-phase engineering of two-dimensional materials

Tuning electrical, optical, and thermal material properties is central for engineering and understanding solid-state systems. In this scenario, atomically thin materials are appealing because of their sensitivity to electric and magnetic gating, as well as to interlayer hybridization. Here, we introduce a radically different approach to material engineering relying on the image interaction experienced by electrons in a two-dimensional material when placed in proximity of an electrically neutral structure. We theoretically show that electrons in a semiconductor atomic layer acquire a quantum phase resulting from the image potential induced by the presence of a neighboring periodic array of conducting ribbons, which in turn modifies the optical, electrical, and thermal properties of the monolayer, giving rise to additional interband optical absorption, plasmon hybridization, and metal-insulator transitions. Beyond its fundamental interest, material engineering based on the image interaction represents a disruptive approach to tailor the properties of atomic layers for application in nanodevices.

Investigations on Mode Analysis of Distributed Bragg Reflector based Hybrid Plasmonic Terahertz Waveguide

Terahertz (THz) technology is emerging field and is fascinating to the researchers who are working with photonics integrated circuits. With technological advancements and developments for various applications, a novel distributed Bragg reflector (DBR) based hybrid plasmonic terahertz waveguide (HPTW) is proposed and designed to operate at 3 THz with Graphene, Gallium Arsenide (GaAs), High-density Polyethylene (HDPE) and Aluminium Gallium Arsenide (AlGaAs) is discussed in this work. To bring the confinement of the THz wave in a small mode area efficiently, a stripe is introduced between graphene and DBR in HDPE. The normalized mode area is decreased to about 3.733 x 10-3 µm2 by reducing the stripe’s width from 20 to 14 µm with a constant of stripe’s height of 1 µm. The Figure of Merit (FOM) and Propagation Length (PL) increases inversely in correspondence with the stripe’s width from 1.4 to 4.8 and 6 to 16.8 µm respectively.

Coupling between Plasmonic and Molecular Excitations: TDDFT Investigation of an Ag-Nanorod/BODIPY-Dye Interaction.

A time-dependent density functional theory (TDDFT) computational approach is employed to study the optical coupling between a plasmonic system (a Ag50 nanorod) and a fluorescent dye (BODIPY). It is found that the BODIPY dye can interact with a plasmonic system in a rather different and selective way according to the mutual orientation of the fragments. Indeed, (i) the plasmon excitation turns out to be sensitive to the presence of the BODIPY transition and (ii) this can lead to amplify or suppress the resonance accordingly to the relative orientation of the corresponding transition dipoles. To understand the coupling mechanism, we analyze the shape of the induced density in real space and the Individual Component Map of the Oscillator Strength (ICM-OS) plots and achieve a simple rationalization and insight on the origin and features of the coupling. The resulting possibility of understanding plasmon/fluorophore interactions by simple qualitative arguments opens the way to a rational design of hybrid (plasmon + dye) systems with the desired optical behavior.

Multilevel Anti-Counterfeiting Based on Covert Structural Features Embedded in Femtosecond-Laser-Treated Gold Nanocluster/Graphene Hybrid Layer.

The conventional nanoscale anti-counterfeiting scheme, exhibiting limited encoding capacity, faces growing challenges of being falsified with the advent of advanced high-resolution equipment. In this study, we propose a multilevel anti-counterfeiting device based on a femtosecond laser (fs-laser) treated plasmonic gold nanocluster/graphene (AuNC/Gr) hybrid structure integrated with a resonant cavity. The covert structural features encoded in random colored patterns, optical reflection spectra, and Raman spectra constitute three classes of anti-counterfeiting signatures, which originate from the AuNC-covered Gr, which initiates plasmonic and thermal couplings. The attendant inverted thermal distribution is presumed to confine the structural features to the AuNC-Gr interface while leaving no detectable traces on the surface of AuNC/Gr even under advanced high-resolution equipment. Therefore, the proposed approach achieves multilevel anti-counterfeiting accomplishing physically unclonable functions in the form of random colored patterns, reflection spectra, and Raman spectra. As the first report for realizing remarkable optical modulation (i.e., random colored patterns) without any surface trace or damage via fs-laser-AuNC/Gr interaction, our study also discloses the outstanding performance of Gr in fs-laser-induced optothermoplasmonic lithography on near-percolation metal films. Simultaneously, the demonstrated fs-laser-processed plasmonic hybrid structure in conjunction with a resonant cavity is anticipated to expand the encoding capabilities for nanoscale anti-counterfeiting while avoiding the risk of being imitated because of the covert structural features.

Plasmonic hybridization properties in polyenes octatetraene molecules based on theoretical computation

Relationship of plasmonic properties of multiple clusters to molecular interactions and properties of a single cluster or molecule have become increasingly important due to the continuous emergence of molecular and cluster devices or systems. A hybrid phenomenon similar to plasmonic nanoparticle hybridization exists between two molecules with plasmon excitation modes. We use linear-response time-dependent density functional theory, real-time propagation time-dependent density functional theory, the plasmonicity index, and transition contribution maps (TCMs) to identify the plasmon excitation modes for the linear polyenes octatetraene with –OH and –NH2 groups and analyze the hybridization characteristics using charge transitions. The results show that molecular plasmon hybridization exists when the two molecules are coupled. The TCM analysis shows that the plasmon modes and hybridization result from collective and single-particle excitation. The plasmon mode is stronger, and the individual properties of the molecules are maintained after coupling when there is extra charge depose in the molecules because the electrons are moving in the molecules. This study provides new insights into the molecular plasmon hybridization of coupled molecules.

Plasmonic Hybrid Nanostructures in Photocatalysis: Structures, Mechanisms, and Applications.

(Sun)Light is an abundantly available sustainable source of energy that has been used in catalyzing chemical reactions for several decades now. In particular, studies related to the interaction of light with plasmonic nanostructures have been receiving increased attention. These structures display the unique property of localized surface plasmon resonance, which converts light of a specific wavelength range into hot charge carriers, along with strong local electromagnetic fields, and/or heat, which may all enhance the reaction efficiency in their own way. These unique properties of plasmonic nanoparticles can be conveniently tuned by varying the metal type, size, shape, and dielectric environment, thus prompting a research focus on rationally designed plasmonic hybrid nanostructures. In this review, the term "hybrid" implies nanomaterials that consist of multiple plasmonic or non-plasmonic materials, forming complex configurations in the geometry and/or at the atomic level. We discuss the synthetic techniques and evolution of such hybrid plasmonic nanostructures giving rise to a wide variety of material and geometric configurations. Bimetallic alloys, which result in a new set of opto-physical parameters, are compared with core-shell configurations. For the latter, the use of metal, semiconductor, and polymer shells is reviewed. Also, more complex structures such as Janus and antenna reactor composites are discussed. This review further summarizes the studies exploiting plasmonic hybrids to elucidate the plasmonic-photocatalytic mechanism. Finally, we review the implementation of these plasmonic hybrids in different photocatalytic application domains such as H2 generation, CO2 reduction, water purification, air purification, and disinfection.

Polarized Photoluminescence Enhancement of Monolayer MoS2 Coupled with Plasmonic Salisbury‐Type Absorber

AbstractThe plasmon‐mediated manipulation of light–matter interaction in 2D atomically transition‐metal dichalcogenides (TMDs) critically depends on the design of plasmonic nanostructures to achieve the maximum optical field in TMDs. Here, a metal–isolator–metal Salisbury‐type perfect absorber is fabricated to serve as a generator of the localized surface plasmons. The significant photoluminescence (PL) enhancement up to 60‐fold is observed experimentally in the monolayer MoS2 on the top of this gold plasmonic hybrid nanostructures. Furthermore, the PL linear polarization can approach ≈60% around the peak of exciton emission and is independent on the polarization of the excitation laser. This Salisbury‐type plasmon–exciton hybrid system paves a new way to develop optoelectronic devices based on TMDs.

Dual‐Functional Nonmetallic Plasmonic Hybrids with Three‐Order Enhanced Upconversion Emission and Photothermal Bio‐Therapy

AbstractPlasmonic semiconductor nanoparticles (NPs) with wide‐range tailorable localized surface plasmon resonance (LSPR) hold exciting prospects on optical signal amplification. In this work, by precisely controlling oxygen vacancies around W atoms, plasmonic bismuth tungstate Bi2WO6 (BWO) nanosheets are constructed to enhance emission of Yb3+/Er3+ co‐doped NaYF4 upconversion nanoparticles (UCNPs). In the optimal conditions, the UCNPs/BWO‐2 hybrids exhibit over three‐order (1260‐fold) enhancement selectively on the 520 nm emission owing to the strong LSPR‐induced electrical field and photothermal effect. Moreover, it is found that the highly efficient emission of UCNPs/BWO‐2 allows it to act as a thermometer to monitor the real‐time local temperature with high absolute sensitivity of 5.8 × 10−3 K−1 in wide temperature range (up to 990 K). For proof‐of‐concept, the dual functions of plasmonic UCNPs/BWO‐2 hybrids on bioimaging and photothermal therapy for cancer cells are demonstrated that can be completely killed within 5 min under 980 nm irradiation. As far as it is known, this work reaches a new level on UCNPs emission enhancement by plasmonic semiconductor, exceeding most plasmonic metals.

Matrix shaped plasmonic hybrid nanostructure with direction-dependent functionality for multianalyte detection and biosensing

A Surface plasmon resonance based hybrid nanosystem with the competence of single and multiple analytes analysis is demonstrated using a symmetry modified sensory platform for promising application in biosensing. Plasmonic properties of the designed 2 × 2 matrix system arising from higher-order plasmonic modes generated near groove positions in the structure are analyzed numerically and calibrated for enhanced sensor performance and multi-functionality. The asymmetric defect/ percentage of asymmetry (Δ) in the structure, incorporated by means of a position-wise shift of Ag nanodisc exhibits pivotal results in performance parameters, including intra channel sensitivity (S intra), channel separation factor (CH factor ), figure of merit (FOM) and Q-factor. The pairs of sensing windows of the hybrid structure show a geometric symmetry along the x and −x direction and an asymmetry along its perpendicular (y and −y). Among the symmetric and asymmetric channels, spatially resolved plasmonic modes of asymmetric channels facilitate the multi quantification of analytes in a single stimulation, whereas symmetric ones confirm the presence of the different analytes in the given specimen. With the sensor function flexible to light incidence direction, the matrix system can be effectively employed across medical diagnostics and healthcare monitoring.