Hybridization Of Surface Plasmons Research Articles

Hybridization of surface plasmons and photonic crystal resonators for high-sensitivity and high-resolution sensing applications.

In this paper, an optical refractive index (RI) sensor based on a hybrid plasmonic-photonic crystal (P-PhC) is designed. In the sensor's structure, some metallic rods are embedded in a rod-type photonic crystal (PhC) structure. Numerical simulations are performed based on the finite-difference time-domain (FDTD) method. The obtained results illustrate that the localized surface plasmons (LSP) induced by metallic rods can be excited in a PhC lattice to generate a hybrid P-PhC mode. According to the results, the hybrid mode provides unique opportunities. Using metallic rods in the coupling regions between waveguides and the resonant cavity significantly increases the interaction of the optical field and analyte inside the cavity. The simulation results reveal that high sensitivity of 1672nm/RIU and an excellent figure of merit (FoM) of 2388 RIU-1 are obtained for the proposed hybrid P-PhC sensor. These values are highest compared to the purely plasmonic and or purely PhC sensors reported in the literature. The proposed sensor could simultaneously enhance sensitivity and FoM values. Therefore, the proposed hybrid P-PhC RI sensor is a more fascinating candidate for high-sensitivity and high-resolution sensing applications at optic communication wavelengths.

Multiple plasmon-induced transparency based on black phosphorus and graphene for high-sensitivity refractive index sensing.

A hybrid bilayer black phosphorus (BP) and graphene structure with high sensitivity is proposed for obtaining plasmon-induced transparency (PIT). By means of surface plasmon resonance in the rectangular-ring BP structure and ribbon graphene structure, a PIT effect with high refractive index sensitivity is achieved, and the surface plasmon hybridization between graphene and anisotropic BP is analyzed theoretically. Meanwhile, the PIT effect is quantitatively described using the coupled oscillator model and the strong coherent coupling phenomena are analyzed by adjusting the coupling distance between BP and graphene, the Fermi level of graphene, and the crystal orientation of BP, respectively. The simulation results show that the refractive index sensitivity S = 7.343 THz/RIU has been achieved. More importantly, this is the first report of tunable PIT effects that can produce up to quintuple PIT windows by using the BP and graphene hybrid structure. The high refractive index sensitivity of the quintuple PIT system for each peak is 3.467 THz/RIU, 3.467 THz/RIU, 3.600 THz/RIU, 4.267 THz/RIU, 4.733 THz/RIU and 6.133 THz/RIU, respectively, which can be used for multiple refractive index sensing function.

Surface plasmon hybridized dressed states

Surface plasmon hybridization provides new perspectives for light manipulation at the nanoscale and related applications in nanophotonics. Multiple hybridization between metallic layers inside plasmonic nanocavities displays properties similar to atomic dressed states. In this Letter, we propose to numerically and analytically investigate the case of a multilayer structure composed of stacked metallic (M) and insulator (I) thin films. For a small number of MIM blocks, the system shows discrete hybridization schemes arising from plasmonic strong coupling. When the number of layers increases, multiple and stronger couplings occur and give birth to new modes which merge to form a plasmonic energy continuum. A schematic diagram of modes construction is presented to help the design of vertical nanocavities with specific properties such as plasmonic guiding.

Design of a novel polarization insensitive pentaband THz metamaterial

AbstractThis paper presents the design and characterization of a novel metamaterial with five distinct operating bands for THz applications. The proposed metamaterial is constructed using an ultra‐thin polyimide substrate. The proposed metamaterial has a square geometry with metallic patterns suitably designed to obtain the desired frequency characteristics. The metamaterial operates based on surface plasmon hybridization with stopband characteristics at 0.82, 1.96, 2.77, 3.40 and 4.74 THz. The metamaterial has a small geometry 0.082λo × 0.082λo where λo is wavelength calculated under free‐space conditions at 0.82 THz. The operation of the proposed pentaband metamaterial is described using electric field distributions. The metamaterial reported in this paper has rotational symmetry and hence it is polarization independent. The performance of the metamaterial for various angles of incidence has been evaluated and the results reveal that the proposed metamaterial is stable up to ±70 degrees. The THz metamaterial is appropriate for components like frequency selective surface, sensors and detectors.

Concentric designer plasmon hybridization in deep subwavelength metamaterial resonator

Concentric spoof surface plasmon hybridization in the microwave frequency is physically realized with subwavelength plasmonic metamaterials. The hybridization is generated with two concentric spoof localized surface plasmon (LSP) particles, where the overlap of the two spoof LSP particles could be tuned to manipulate the resonance. Such spoof plasmon hybridization could increase the Q factor effectively up to 965, and decrease the electric dimension of the particle down to 1/7 wavelength. The coupled-resonator circuit theory is applied to analyze the interaction mechanism of the structure with strong electric and magnetic coupling. Near electric-field distributions are mapped in the simulation and experiment to characterize the resonant property. Both the bonding mode and the antibonding mode are observed. A free space measurement system is adopted to improve the measurement of the spoof LSP resonant spectra.

Near-field radiative heat transfer in graphene plasmonic nanodisk dimers

Near-field thermal radiation mediated by surface plasmons in parallel graphene nanodisk dimers is studied using a semianalytical model under the electrostatic approximation. The radiative heat transfer between two disks as a function of the distance between them in coaxial and coplanar configurations is first considered. Three regimes are identified and their extents determined using nondimensional analysis. When the edge-to-edge separation is smaller than the disk diameter, near-field coupling and surface plasmon hybridization lead to an enhancement of the radiative heat transfer by up to four orders of magnitude compared to the Planck blackbody limit. A mismatch in the disk diameters affects the plasmonic mode hybridization and can either diminish or enhance the near-field radiation. Destructive interference between eigenmodes that emerge when the relative orientation between disks is varied can induce a twofold reduction in the radiative heat transfer. In all configurations, the radiative heat transfer properties can be controlled by tuning the disk size/orientation, the substrate optical properties, and graphene's doping concentration and electron mobility.

Plasmonic Nanolenses: Electrostatic Self-Assembly of Hierarchical Nanoparticle Trimers and Their Response to Optical and Electron Beam Stimuli.

Asymmetric nanoparticle trimers composed of particles with increasing diameter act as "plasmonic lenses" and have been predicted to exhibit ultrahigh confinement of electromagnetic energy in the space between the two smallest particles. Here we present an electrostatic self-assembly approach for creating gold nanoparticle trimers with an assembly yield of over 60%. We demonstrate that the trimer assembly leads to characteristic red-shifts and show the localization of the relevant plasmon modes by means of cathodoluminescence and electron energy loss spectroscopy. The results are analyzed in terms of surface plasmon hybridization.

Theoretical study of photoinduced charge transfer in molecule and multi-metalnanoparticles system

Photoinduced enhancement effect of the metal nanoparticle is one of the hot topics in the field of nanomaterial. Interaction between one molecule and a number of metal nanoparticles in different configurations in an applied external field is theoretically investigated in the scheme of density matrix theory, where the molecule and metal nanoparticles are excited simultaneously, and the subsequent charge transfer dynamics is simulated. Besides, the Coulomb interactions between the molecule and metal nanoparticles are calculated in the framework of dipole-dipole approximation. Parameters for metal nanoparticles with a 10 nm radius are used in the text and the polarization of the molecule has the same direction as that of external laser field. It is found that plasmon enhancement is closely related to the relative positions between the molecule and metal nanoparticles. Effects of enhancement due to the surface plasmon is discussed in detail for different configurations of the molecule and metal nanoparticles, and the surface plasmon hybridization, as well as the molecular excitation energy and the frequency of external field applied. Plasmon hybridization levels are formed when metal nanoparticles have strong enough interactions between themselves. The blue shift of the resonant frequency can be found for shorter distance of different metal nanoparticles. In the case that the centers of mass of metal nanoparticles and the molecule are on the same plane, it is found that the population in excited state of the molecule at a resonance frequency increases for a shorter distance between metal nanoparticles and the molecule. On the contrary, in the case that the centers of mass of four metal nanoparticles are located in a plane which is parallel to the x-y plane and above it by 10 nm, the population in the excited state of the molecule on resonant frequency will decrease at a shorter distance between the four metal nanoparticles.

Extreme blueshift of surface plasmon resonance frequency in graphene nanodisk stacks

The extraordinary properties of graphene surface plasmons like strong field confinement, long propagation distance and tunability have made graphene an attractive alternative to noble metals. However, it is still experimentally challenging to increase the resonance frequency in graphene nanostructures beyond the mid-IR limit. In this work, we investigate the blueshift of surface plasmon resonance frequency via plasmon hybridization in graphene disk stacks. Based on a nonretarded approach, we study the plasmon hybrid modes in graphene disk stack structures, considering the optical coupling between the uncouple eigenmodes of each disk. Through this methodology we were also able to extract the scattered and absorbed fields. We find that due to plasmon hybridization in an N-disk stack, each uncoupled mode splits into N hybrid modes. When the distance between disks is close to the strong coupling limit, we observe that for each uncoupled mode there is only one hybrid mode that is blue-shifted compared with the resonance frequency of its respective uncoupled mode. Analysis of the hybridization by reducing the distance between disks shows that in the transition between the weak and strong coupling regimes the interaction is mainly driven by the coupling of edge plasmons. For a stack with 25 graphene disks having a Fermi level of 1.0eV and a 50nm disk diameter, we observe that surface plasmon hybridization can effectively blueshift the resonance frequency up to 0.69eV (1.8μm). In addition, compared to a single graphene disk with the same diameter, the 25-disk stack can increase the peak of absorption and scattering cross sections by 12 and 38 times, respectively, opening up a wide range of applications for graphene surface plasmons in the near-infrared regime.

Fractal H-shaped plasmonic nanocavity

Based on complementary fractal geometry structures, we design a novel infrared quasi-three-dimensional (3D) nanocavity with a localized enhanced field with multiband resonant frequencies. The fractals offer the nanostructure two important characteristics, multiband functionality and a subwavelength effect. The electric field, power flow, and the field intensity distributions are given to indicate the internal mechanism of the localized enhanced field in the nanocavity. Additionally, the effective medium method is established to retrieve the permittivity and impedance of the structure. It is shown that a strongly enhanced localized field is achieved in the nanocavity at two different resonant frequencies by using the finite difference time domain method. The field intensity in the nanocavity is enhanced by a factor of up to 60 times over that of the incident light because of the important contribution of the loss factor in the permittivity. The surface plasmon hybridization is thought to play an important role in the strong localized field enhancement. The multiband property and high localized intensity offer the nanocavity great potential for applications in surface enhanced Raman scattering and other nanoscale novel devices.

Surface plasmon hybridization and exciton coupling

We derive a semianalytical model to describe the interaction of a single photon emitter and a collection of arbitrarily shaped metal nanoparticles. The theory treats the metal nanoparticles classically within the electrostatic eigenmode method, wherein the surface plasmon resonances of collections of nanoparticles are represented by the hybridization of the plasmon modes of the noninteracting particles. The single photon emitter is represented by a quantum mechanical two-level system that exhibits line broadening due to a finite spontaneous decay rate. Plasmon-emitter coupling is described by solving the resulting Bloch equations. We illustrate the theory by studying model systems consisting of a single emitter coupled to one, two, and three nanoparticles, and we also compare the predictions of our model to published experimental data.

Giant Enhancement of Light Emission from Au Nanocrystals into a Porous Matrix Integrated with Silicon Platform

Integration of metal nanoparticle-dielectric films with silicon technology is emerging as a promising candidate for sub-wavelength optoelectronics and correlated devices. A giant enhancement of the luminescence intensity of gold nanocrystals directly prepared on a nanoporous template of anodized aluminium oxide is evaluated herewith, for the first time in literature, as a favourable substrate for integrating silicon-based optoelectronics. The size and lateral separation between adjacent particles are controlled by the geometry of the dielectric matrix and on-chip-integration is achieved during the nanoparticle growth, requiring no further steps. A more pronounced photoresponse is observed with embedded nanocrystals as small as 12 nm and the high emission is attributed to the light confinement associated to the increase of the local field effect on the surface plasmon hybridization waves. The demonstrated ability to control the assemble of the nanocrystals and the intense light emission indicate that the embedded gold nanostructures have a high potential for plasmonic device applications.