Surface Plasmon Coupling Research Articles

Biomaterial actuator of M13 bacteriophage in dynamically tunable plasmonic coupling structure

Nano-gap plasmonic nanostructures like nanoparticle on a metallic film (NPOM) exhibit enhanced near-field properties because of surface plasmon coupling. Utilizing metallic NPs shape, size, material choice, and dielectric film-induced nano-gap (or hot-spots), it is possible to exploit potential applications in sensors. To achieve dynamic sensing, the application of tunable nano-gaps in response to external stimuli has been attempted using biopolymers. M13 bacteriophages are viable candidates as nano-gap materials owing to their widely adjustable physicochemical properties by genetic engineering technology. Here, we demonstrate a collective light-scattering spectrum of the surface-enhanced plasmonic resonance characterized by the surface morphology of the employed M13 bacteriophage thin film. Our NPOM (Ag nanocube/M13 bacteriophage film/Au film) nanostructure revealed differences in experimental and simulated scattering peak wavelength shift when nano-gap size(s) are varied. An AFM (Atomic Force Microscopy) surface morphology analysis of the M13 bacteriophage film showed its non-uniform thickness distribution explaining the differences in scattering peak wavelength properties. We confirmed that the M13 bacteriophage performs well as a sensor based on static and dynamic moisture exposure. Benefitting from the adaptability and sensitivity of the M13 biomaterial, our gap plasmonic coupling structure can be used for sensing VOCs as a biosensor.

Covalent and noncovalent hybrids of di-amino porphyrin functionalized graphene oxide and their interaction with gold nanoparticles

Porphyrin functionalization of graphene oxide (GO) influenced the plasmonic effect of gold nanoparticles (AuNP). The former was achieved by modification of GO with 5,10-bis(4-aminophenyl)-15,20-diphenylporphyrin, P(NH2)2,adj, by noncovalent interactions as well as by covalent association, following standard chemistry. The success of the chemical functionalization of GO with P(NH2)2,adj, was confirmed by FTIR. Steady-state and time-resolved fluorescence showed a strong fluorescence quenching of porphyrin in the presence of GO, indicative of a photoinduced electron transfer process from porphyrin units to GO, which acts as an electron acceptor. The surface plasmon coupling effect promoted by the AuNP@GO hybrids, proved to be effective only in the case of the noncovalent hybrid, detected through the decrease of the porphyrin fluorescence lifetime and increase in the emission intensity in solution, in good agreement with FLIM results on deposited samples.

Enhanced Resonant Energy Transfer by Decorating Au Nanoparticles on the Sidewalls of InGaN Multiple‐Quantum‐Well Nanorods

An enhanced resonant energy transfer (RET) process between green InGaN multiple quantum wells (MQWs) and CdSe/ZnS quantum dots (QDs) is investigated by decorating the sidewalls of InGaN MQW nanorods with Au nanoparticles. The InGaN MQW nanorods are shallow‐etched to the region of InGaN MQWs or deep‐etched through InGaN MQWs completely. The Au nanoparticles can provide localized surface plasmon coupling to both InGaN MQWs and QDs, leading to accelerated decay rates. The localized surface plasmons also enhance the RET process between InGaN MQWs and QDs. Compared to the bare nanorods without Au nanoparticles, the enhancement factors of the RET process are 1.8 and 5.6 for shallow‐ and deep‐etched MQW nanorods, respectively. The larger enhancement factor for deep‐etched nanorods is mainly attributed to the weaker localized surface plasmon coupling with InGaN MQWs, which is proposed to compete with the RET process. The RET efficiency in the deep‐etched InGaN MQW nanorods is calculated as 62%, demonstrating high potential for usage in energy conversion devices.

Flexible nanoparticle-on-mirror strategy for ultrasensitive molecule detection by directionally coupling surface plasmon polaritons

Applying local surface plasmon resonance (LSPR) to a nanoparticle-on-mirror (NPOM) configuration for realizing highly sensitive molecule detection using surface-enhanced Raman scattering (SERS) typically enhances the Raman signal by 106–1010 under limiting conditions. We propose a special nanoparticle-fishbone structure (NPFS) system, which incorporates the surfaceplasmon polariton (SPP) coupler of the fishbone structure into the NPOM configuration, to achieve ultra-high local electric field enhancement by plasmon hybridizing the LSPR mode of metallic nanoparticles and the SPP mode of the fishbone array structure. During the numerical simulation, the NPFS system exhibited a SERS enhancement factor of 1011, which is two orders of magnitude higher than that of the NPOM system; the SERS experimental results further demonstrated its outstanding performance. These findings indicate that introducing a well-designed SPP coupler on the metallic film can further improve the advantages of various NPOM configurations. The proposed approach can open new horizons for designing nanoscale photonic devices for ultrasensitive molecule detection.

Numerical study of vegetable oil as dielectric in the generation of surface plasmon polaritons in metal: The case of double interfaces

Modified electromagnetic waves which is resulted from coupling of surface plasmon and initial electromagnetic waves are called surface plasmon polaritons (SPP). These type of polaritons are generated at the interface between metal and dielectric. Many studies are performed since SPP have potential application in many fields. The process of generating SPP was usually using dielectrics in the form of solid. However, the usage of liquid dielectric in generating SPP is very rare. In this study, we predict numerically the usage of liquid dielectrics by solving the dispersion relation of the SPP. The dispersion relation was derived using Maxwell equations and the continuity of the fields at the interfaces. The metal was immersed in the liquid dielectrics. We used parameters of castor oil as liquid dielectric in the numerical calculation. We found that the dispersion relation had two branches. One branch represented in phase condition while the other branch illustrated out of phase condition. This result agree with the previous research using solid dielectric.

A polarization-resolved ECL strategy based on the surface plasmon coupling effect of orientational Au nanobipyramids patterned structures

Here, we developed a polarization-resolved surface plasmon coupling electrochemiluminescence (ECL) strategy based on orientational Au nanobipyramids (Au NBPs) patterned structures. As the surface plasmonic materials, the Au NBPs with large localized electromagnetic field enhancement were used to construct the different patterned structures through the droplet evaporation induced assembly. The distinct morphology of the horizontal and vertical Au NBPs patterned structures provided the different plasmonic properties reflecting on resonance peak positions and polarized absorbance. As a result, the variations of the polarized ECL emission of SnS2 QDs have been regulated by the Au NBPs patterned structures via the surface plasmon coupling progress. Because of the superior polarization-resolved ECL performances, the sensing system was used to analyze the miRNA-21 and miRNA-205 expression level in tumor tissues of triple negative breast cancer patients. The satisfactory results indicated this polarization-resolved sensing strategy possessed great potential for clinical analysis.

Resonant enhancement of photoluminescence from dye molecules in lithium niobate substrate using photoinduced silver deposition with concentration dependence

This work fabricates a plasmonic lithium niobate substrate with metal nanoparticles (MNPs) to enhance electromagnetic field interaction and diminish lifetime with concentration dependence. The enhanced photoluminescence (PL) from dye molecules in lithium niobate substrate and shortened lifetimes associate with plasmon resonance arising from the metal nanoparticles (MNPs) layers. We experimentally and numerically verified that the surface plasmon coupling between MNPs potentially influences PL reactions. The remarkable enhanced PL of deposited MNPs substrate can be achieved by increasing absorption. The fabricated structure can help tune the surface-enhanced electromagnetic field. The Raman signal of rhodamine 6G dye and PL intensity of DCJTB (4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran) molecules in the fabricated substrate are enhanced 13 times and 10.26 times compared to untreated. Besides, the lifetime is reduced by 22.63%. This work is a perspective method for designing a PL-active lithium niobate substrate using photoinduced metal deposition with concentration dependence.

Quantum Dot-Induced Blue Shift of Surface Plasmon Spectroscopy.

We experimentally demonstrate the spectral blue shift of surface plasmon resonance through the resonant coupling between quantum dots (QDs) and surface plasmons, surprisingly in contrast to the conventionally observed red shift of plasmon spectroscopy. Multimode optical fibers are used for extended resonant coupling of surface plasmons with excited states of QDs adsorbed to the plasmonic metal surface. The long-lived nature of excited QDs permits QD-induced negative change in the local refractive index near the plasmonic metal surface to cause such a blue shift. The analysis utilizes the physical causality-driven optical dispersion relation, the Kramers–Kronig (KK) relation, attempting to understand the abnormal behavior of the QDs-induced index dispersion extracted from blue shift measurement. Properties of QDs’ gain spectrally resonating with plasmons can account for such blue shift, though their absorbance properties never allow the negative index change for the blue shift observed according to the KK relation. We also discuss the limited applicability of the KK relation and possible QDs gain saturation for the experiment–theory disagreement. This work may contribute to the understanding of the photophysical properties critical for plasmonic applications, such as plasmonic local index engineering required in analyte labeling QDs coupled with plasmons for biomedical imaging or assay.

Perspective on plexciton based on transition metal dichalcogenides

Two-dimensional transition metal dichalcogenides (TMDCs) have outstanding physical advantages over graphene-like non-zero bandgap structures. It indicates that the monolayer TMDC material has significant light–material interaction, and it also implies that TMDCs have various application prospects in optoelectronic devices. The coupling of excitons and metal surface plasmons in monolayer TMDCs would affect the optical and electrical properties of the TMDC surface, and we revealed the improvement of surface catalytic reaction efficiency by plexcitons (coupling of excitons and plasmons) supported by recent experiments and theoretical reports. We also review the stress regulation on charge transfer excitons based on van der Waals (vdW) heterostructures composed of TMDCs, the special characteristics, and potential applications of coupling charge-transfer excitons with Ag plasmons in vdW and lateral heterostructures.

Theoretical Investigation of Coupling of Surface Plasmons in One-dimensional Periodic Structure of SiO2 and TiO2 with Defect of Nanocomposite of Liquid Crystals and Core–Shell Nanoparticles

Theoretical Investigation of Coupling of Surface Plasmons in One-dimensional Periodic Structure of SiO2 and TiO2 with Defect of Nanocomposite of Liquid Crystals and Core–Shell Nanoparticles

Surface Plasmon Coupling of Ag Nanoparticles with InGaN/GaN Quantum Wells for Enhancing the Emission Efficiency of Light-Emitting Devices

Surface Plasmon Coupling of Ag Nanoparticles with InGaN/GaN Quantum Wells for Enhancing the Emission Efficiency of Light-Emitting Devices

Ge20Sb15Se65 glass-based ultra-bandwidth X-shaped dual-core photonic crystal fiber polarization beam splitter with an air hole filled gold rod

In this paper, a novel X-shaped dual-core photonic crystal fiber polarization beam splitter (X-DC-PCF PBS) with an air hole filled gold rod based on G e 20 S b 15 S e 65 glass is proposed. According to the DC mode coupling theory and surface plasmon resonance effect, the mode coupling phenomena of the x polarization (X-pol) and y polarization (Y-pol) odd and even modes are analyzed, respectively. The variation laws of coupling lengths of the X-pol and Y-pol and the coupling length ratio with different structural parameters at wavelength 1.55 µm are investigated. When the shortest polarization splitting length ( L P S ) is 230 µm, there is only the X-pol and Y-pol light in the cores A and B, respectively. By considering the variation of the extinction ratio and insertion loss (IL) with wavelength, the final polarization splitting bandwidth (PSB) is 358 nm (1.367–1.725 µm), and the maximum ILs of the X-pol and Y-pol in the whole PSB are 0.04 and 0.8 dB, respectively. The proposed X-DC-PCF PBS has ultra-wide PSB, short L P S , and ultra-low IL, so it will play an important role in the development of optical integration technology and the construction of an all-fiber loop platform.

Thinfilm Hybrid Nanostructures: A Perspective to Subcycle Opto-Electronics and Coherent Control

In this article we present a theoretical investigation of gold-silica-silver nanostructures and their optical properties with respect to ultrafast electronic applications and coherent control by tailored optical fields. We found a remarkable sensitive behavior to the carrier envelope phase (CEP) of the driving laser pulses in the coupling of surface and bulk plasmons leading to a superposition of distinct modes with a time-dependent amplitude structure. Furthermore, we show a rather complex temporal evolution of plasmonic surface modes. Our results suggest the potential for coherent control of the time-dependent resonant coupling between surface and volume modes by tailored laser pulses and foster the field of time-dependent spectroscopy of thinfilm hybrid nanostructures with single layer thickness down to the two-dimensional limit.

Analysis and optimization of graphene based reconfigurable electro-optical switches

We consider a planar layered structure including a graphene sheet with an unexpected transmission of the beam in total internal reflection angles. In this paper, we investigate this particular response through the excitation of leaky type surface plasmons of graphene and the coupling of surface plasmons to far-field radiations. Dependence of the transmission on the chemical potential of graphene is investigated and maximized by optimization techniques. Thus, for a fixed frequency and angle of incident beam, the transmission coefficient can be set between 0 and a maximum value (up to more than 0.9) by tuning the chemical potential of graphene via the applied voltage. This effect can be used in design of tunable optoelectronic frequency/angle switches.

Enhancement of the Modulation Response of Quantum-Dot-Based Down-Converted Light through Surface Plasmon Coupling.

In this paper, we first elaborate on the effects of surface plasmon (SP) coupling on the modulation responses of the emission of a light-emitting diode (LED) and its down-converted lights through colloidal quantum dots (QDs). The results of our past efforts for this subject are briefly discussed. The discussions lay the foundation for the presentation of the new experimental data of such down-converted lights in this paper. In particular, the enhancement of the modulation bandwidth (MB) of a QD-based converted light through SP coupling is demonstrated. By linking green-emitting QDs (GQDs) and/or red-emitting QDs (RQDs) with synthesized Ag nano-plates via surface modifications and placing them on a blue-emitting LED, the MBs of the converted green and red emissions are significantly increased through the induced SP coupling of the Ag nano-plates. When both GQD and RQD exist and are closely spaced in a sample, the energy transfer processes of emission-reabsorption and Förster resonance energy transfer from GQD into RQD occur, leading to the increase (decrease) in the MB of green (red) light. With SP coupling, the MB of a mixed light is significantly enhanced.

Enhanced Near-Field Radiative Heat Transfer between Graphene/hBN Systems.

Near-field radiative heat transfer (NFRHT) can exceed the blackbody radiation limit owing to the coupled evanescent waves, implying a significant potential for energy conversion and thermal management. Coupled surface plasmon polaritons (SPPs) and hyperbolic phonon polaritons (HPPs) with small ohmic losses enable a long propagation wavelength that is essential in NFRHT. However, so far, there still lacks knowledge about the experimental investigation of the coupling of SPPs and HPPs in terms of NFRHT. In this study, the NFRHT between graphene/hexagonal boron nitride (hBN) systems that can be readily transferred onto various substrates, with a gap space of ≈400nm is measured. NFRHT enhancements in the order of three and six times higher than the blackbody limit for graphene/hBN heterostructures and graphene/hBN/graphene multilayers, respectively are demonstrated. In addition, the largest ever radiative heat flux using graphene/hBN/graphene multilayers under similar gap space of 400nm is obtained. Consequently, analyzing the photon tunneling modes reveal that these phenomena are consequences of coupled SPPs of graphene and HPPs of hBN.

A novel doublet-based surface plasmon resonance biosensor via a digital Gaussian filter method

In this paper, a digital Gaussian filter coupled surface plasmon resonance (SPR) sensor with a doublet was proposed to enhance the sensing performance of conventional SPR sensor. The shift of central angle calculated from doublet was employed instead of the shift of resonance angle obtained from SPR curve. Expected angle and FWHM (full width at half maximum) are two parameters for the post-processing Gaussian model. The refractive index (RI) sensitivity has a symmetry relationship with expected angle and the reversed maximum sensitivity is usually larger than that of forward maximum. The reversed maximum sensitivity increases first and then decreases when increasing FWHM from 0.2 to 20 deg. Further, a dynamic and adjustable Gaussian model was employed to satisfy the large sensing range need. The RI sensitivity as high as 254.21 deg/RIU was obtained, which is nearly 2-fold higher than that of traditional gold-based SPR sensor, that is 131.58 deg/RIU. And thus, the RI resolution was calculated to be 7.16 × 10−6 RIU based on three-fold standard deviation theory. The LOD for rabbit IgG as low as 9.58 ng/mL was achieved and it is nearly 3-fold lower than that of traditional gold-based SPR biosensor, that is 30.64 ng/mL.

All-optical terahertz logic gates based on coupled surface plasmon polariton sub-wavelength waveguiding in bulk Dirac semimetal

Bulk Dirac semimetals (BDS) are quantum fermionic system also identified as three-dimensional counterpart of graphene exhibit rich plasmonic response at terahertz (THz) frequencies. In this work, we report THz waveguiding in the BDS curved geometries, which confine electromagnetic field in the form of symmetrically coupled surface plasmon polariton (SPP) modes. We demonstrate how the sub-wavelength BDS-Air-BDS multilayer system with various bending and corners efficiently confines THz beam with minimal bending losses. The realized sub-wavelength THz waveguiding in BDS system is advantageous than other approaches like zero-refractive index metamaterials. Based on the symmetric coupled SPP waveguiding in BDS multilayers, all-optical logic gates including OR, AND, XOR, NOR and NAND are realized at THz waveband. The realized THz logic gates exhibit optimal threshold transmission (at least 50%) for defining ON-OFF states. We anticipate that the illustrated waveguiding and logic gate applications in BDS system could open an avenue for optoelectronic applications at THz frequencies.

The Role of Molecular Arrangement on the Strongly Coupled Exciton–Plasmon Polariton Dispersion in Metal–Organic Hybrid Structures

Metal–organic hybrid structures have been demonstrated to be a versatile platform to study primary aspects of light–matter interaction by means of emerging states comprising excitonic and plasmonic properties. Here we are studying the wave-vector-dependent photoexcitations in gold layers covered by molecular films of zinc phthalocyanine and its fluorinated derivatives (FnZnPc, with n = 0, 4, 8, 16). These layered metal–organic samples show up to four anticrossings in their dispersions correlating in energy with the respective degree of ZnPc fluorination. By means of complementary structural and theoretical data, we attribute the observed anticrossings to three main scenarios of surface plasmon coupling: (i) to aggregated α-phase regions within the FnZnPc layers at 1.75 and 1.85 eV, (ii) to a coexisting F16ZnPc β-polymorph at 1.51 eV, and (iii) to monomers, preferentially located at the metal interface, at 2.15 eV. Whereas energy and splitting of the monomer anticrossings depend on strength and average tilting of the molecular dipole moments, the aggregate-related anticrossings show a distinct variation with degree of fluorination. These observations can be consistently explained by a change in FnZnPc dipole density induced by an increased lattice spacing due to the larger molecular van der Waals radii upon fluorination. The reported results prove Au/FnZnPc bilayers a model system to demonstrate the high sensitivity of exciton–plasmon coupling on the molecular alignment at microscopic length scales.

Asymmetric optical transmission of a metallic grating-incorporated Fabry–Pérot cavity

In this report, we show a structure of metallic grating-incorporated Fabry–Pérot (F–P) cavity demonstrating asymmetric optical transmission (AOT) for all transmission modes. The asymmetric transmission basically arises from asymmetric coupling and decoupling of resonant surface plasmons (SPs) on both sides of the metallic grating with asymmetric media of different indices. Coupling of the SP mode with anti-resonance mode of the F–P cavity in orthogonal directions further optimizes transmission characteristics of the structure for asymmetric transmission. Particularly, a high contrast AOT is achieved by locating the SP resonance position at center of the anti-resonance band of the F–P cavity. Meanwhile, SP resonance modes induced at different interfaces/regions of the cavity structure influence the transmission properties. The AOT structure has no nanoapertures and critical requirements on profile of the grating surfaces for fabrication, and can be adapted to various optical systems.