Coupled Surface Plasmon Polariton Modes Research Articles

Enhanced Quantum Dot Spontaneous Emission with Multilayer Metamaterial Nanostructures

The Purcell effect of quantum dot (QD) spontaneous emission with Ag-SiO2 multilayer metamaterial nanostructures has been demonstrated in experiment and simulation. A broadband enhanced spontaneous emission rate of QDs is observed due to large local density of states in the epsilon-near-zero and hyperbolic regions of multilayer structures. Multilayer gratings are utilized to further enhance the QD spontaneous emission as the QDs located inside the grating grooves strongly interact with high-k coupled surface plasmon polariton modes. Photoluminescence decay measurements are in good agreement with both analytical treatment with a nonlocal effect and three-dimensional finite-element simulation. Detailed studies of QD position and polarization effects on emission rate enhancement for multilayer and multilayer grating nanostructures provide important insight for understanding the coupling mechanisms of emitter–multilayer interaction and the engineering of local density of states in metamaterial nanostructures. ...

Engineering optical gradient force from coupled surface plasmon polariton modes in nanoscale plasmonic waveguides**Project supported by the National Natural Science Foundation of China (Grant No. 11474106) and the Natural Science Foundation of Guangdong Province, China (Grant No. 2016A030313439).

We explore the dispersion properties and optical gradient forces from mutual coupling of surface plasmon polariton (SPP) modes at two interfaces of nanoscale plasmonic waveguides with hyperbolic metamaterial cladding. With Maxwell’s equations and Maxwell stress tensor, we calculate and compare the dispersion relation and optical gradient force for symmetric and antisymmetric SPP modes in two kinds of nanoscale plasmonic waveguides. The numerical results show that the optical gradient force between two coupled hyperbolic metamaterial waveguides can be engineered flexibly by adjusting the waveguide structure parameters. Importantly, an alternative way to boost the optical gradient force is provided through engineering the hyperbolic metamaterial cladding of suitable orientation. These special optical properties will open the door for potential optomechanical applications, such as optical tweezers and actuators.

Strong coupling between surface plasmon polaritons and emitters: a review

In this review we look at the concepts and state-of-the-art concerning the strong coupling of surface plasmon-polariton modes to states associated with quantum emitters such as excitons in J-aggregates, dye molecules and quantum dots. We explore the phenomenon of strong coupling with reference to a number of examples involving electromagnetic fields and matter. We then provide a concise description of the relevant background physics of surface plasmon polaritons. An extensive overview of the historical background and a detailed discussion of more recent relevant experimental advances concerning strong coupling between surface plasmon polaritons and quantum emitters is then presented. Three conceptual frameworks are then discussed and compared in depth: classical, semi-classical and fully quantum mechanical; these theoretical frameworks will have relevance to strong coupling beyond that involving surface plasmon polaritons. We conclude our review with a perspective on the future of this rapidly emerging field, one we are sure will grow to encompass more intriguing physics and will develop in scope to be of relevance to other areas of science.

Nonlocal Effects on Optical Gradient Force from Coupled Surface Plasmon Polaritons in Wire Medium Waveguides

We analytically study optical gradient forces from the mutual coupling between surface plasmon polariton (SPP) modes at the interfaces of two wire medium metamaterial waveguides separated by a linear dielectric. Based on the nonlocal model, dispersion properties and optical gradient forces from coupled SPP modes are analyzed mainly and compared with the local case. The forces from the coupled SPP modes are calculated by Maxwell stress tensor. Numerical results show that the nonlocal effects on dispersion properties and optical forces are very large, especially in the case of large propagation constant, and that symmetric (antisymmetric) SPP modes give rise to an attractive (repulsive) interaction, respectively. In addition, the nonlocal effects on the cutoff frequency for the antisymmetric SPP modes are clarified. These properties indicate that the force from the coupled SPPs at wire medium metamaterials offer another avenue for controlling the growth and self-assembling of artificial metamaterials.

Dispersion relations for coupled surface plasmon-polariton modes excited in multilayer structures

The coupled surface plasmon-polariton (SPP) modes excited in an Al/SiO2/Al multilayer structure were analyzed using angle-resolved electron energy-loss spectroscopy (AREELS) with a relativistic electron probe. The dispersion relations for the coupled SPP modes were then directly observed and compared with predicted relations obtained via calculations. Good agreement was noted between the experimental and calculated results. In the multilayer structures, the dispersion relation for the coupled SPP modes was found to be sensitive to the thickness of each film, which could be interpreted qualitatively by the electron energy-loss probability calculated for thin aluminum (Al) films and narrow Al gaps using Kröger's formula. It was demonstrated that significant differences in the excitation probability for SPPs could be observed depending on the coupling modes.

Equi-Reflectance Dual Mode Resonance Using Bimetallic Loaded Dielectric Plasmonic Structure

Theoretical study of the reflectance response of an asymmetrically-clad bimetallic film that supports coupled surface plasmon polariton modes has been presented. Through adjusting the relative thickness of the two metal film components, the relative coupling strength to the long range (LR) and short range plasmon modes can be altered. It is possible to obtain optimal and equi coupling (zero reflectivity) to both modes for given incident wavelength by further adjusting the overall thickness of bimetallic film. Simultaneous angular and spectral sensitivity calculations of resonance of the LR mode have been demonstrated for sensing application. Tailoring of the structure of individual metal films realizing equi- and non-equi-reflectance modes has been proposed which may further be used for plasmonic trinary logic using binary di-bit images.

Coupled SPP Modes on 1D Plasmonic Gratings in Conical Mounting

Plasmonic nanostructures exhibit a variety of surface plasmon polariton (SPP) modes, with different characteristic properties. While a single metal dielectric interface supports a single-interface SPP mode, a thin metal film can support extended long range SPPs and strongly confined short range SPPs. When the coupling between the incident light and the SPP is provided through a diffraction grating, it is possible to azimuthally rotate the grating with respect to the scattering plane, introducing the possibility to propagate the SPP along an arbitrary direction. We present a theoretical and experimental analysis of the coupling conditions for long range and short range SPPs under this configuration. We also investigate the propagation length of the modes depending on the propagation direction with respect to the grating grooves, showing in particular that the long range SPP propagation length can be sensibly enhanced with respect to the null-azimuth case.

Coupled Surface Plasmon-Polariton Modes of Metallic Single-Walled Carbon Nanotubes

The propagation of the coupled surface plasmon-polariton modes in the metallic single-walled carbon nanotubes are investigated, taking into account the retardation effects. A simple model based on the classical electrodynamics and the two-fluid hydrodynamic theory is proposed. The dispersion relation of the surface polariton modes is obtained in order to survey the effects of the two-fluid model and the insulating dielectric media.

Propagation characteristics of coupled surface plasmon polaritons in PVDF slab waveguides at terahertz frequencies

We present the propagation characteristics of y-polarized coupled surface plasmon polariton (SPP) modes supported by ferroelectric polyvinylidene fluoride (PVDF) slab waveguides at terahertz (THz) frequencies. Employing a two-dimensional (2D) finite-element method, four y-polarized coupled SPP modes are obtained, where two modes exhibit long propagation lengths (∼700 μm) and the others provide subwavelength confinement. It is shown that PVDF is a promising material for plasmon-like excitation in the terahertz regime and results in strong confinement of THz wave propagation in SPP-based coupled waveguides.

Dynamics of coupled plasmon polariton wave packets excited at a subwavelength slit in optically thin metal films

We study by numerical simulations the excitation and propagation dynamics of coupled surface plasmon polariton (SPP) wave packets (WPs) in optically thin Ag films and a bulk Ag/vacuum interface under the illumination of a subwavelength slit by 400 nm continuous wave (cw) and femtosecond pulsed light. The generated surface fields include contributions from both SPPs and quasicylindrical waves, which dominate in different regimes. We explore aspects of the coupled SPP modes in Ag thin films, including symmetry, propagation, attenuation, and the variation of coupling with incident angle and film thickness. Simulations of the electromagnetic transients initiated with femtosecond pulses reveal new features of coupled SPP WP generation and propagation in thin Ag films. Our results show that, under pulsed excitation, the SPP modes in an Ag thin film break up into two distinct bound surface wave packets characterized by marked differences in symmetries, group velocities, attenuation lengths, and dispersion properties. The nanometer spatial and femtosecond temporal scale excitation and propagation dynamics of the coupled SPP WPs are revealed in detail by movies recording the evolution of their transient field distributions.

Modal characteristics of coupled metallic nanoscale rectangular apertures

We examine the modal characteristics of coupled metallic nanoscale rectangular apertures using a simple and accurate separation of variables method, recently proposed by us for a single aperture [Opt. Lett.33, 333 (2008)]. The study shows that the coupling between the antisymmetric surface plasmon polariton (SPP) modes of the two rectangular apertures results in a coupled SPP mode with very large propagation length, larger than 1 mm at the wavelength of 0.633 microm, provided the aperture size and the separation are sufficiently large. The effective indices and the propagation lengths of various coupled SPP modes are presented.

Spontaneous emission from within a metal-clad cavity mediated by coupled surfaceplasmon–polaritons

The emission of light from within a sub-wavelength metal-clad cavity is investigated.We find that emitters placed inside such a cavity emit into the coupled surfaceplasmon–polariton mode supported by this structure. We use grating structures to couplethe non-radiative coupled surface plasmon–polariton modes to light and present the resultsof measurements of photoluminescence from such structures in the form of dispersioncurves. We discuss our findings in the context of sub-wavelength cavities as a means tocontrol the emission of light.

Plasmonic effects in near-field optical transmission enhancement through a single bowtie-shaped aperture

In this paper, the enhanced optical transmission through a special type of aperture of a bowtie shape is investigated through near-field imaging and finite-difference numerical analysis. Under linear polarizations in two orthogonal directions, the optical near fields of the bowtie aperture and comparable square and rectangular apertures made in gold and chromium thin films are measured and compared. The bowtie aperture is able to provide a nanometer-sized optical spot when the incident light is polarized across the bowtie gap and delivers a considerable amount of light. Localized surface plasmons are clearly observed in the near-field images for both bowtie and rectangular apertures in gold, but invisible in chromium. Finite-difference time-domain calculations reveal that, depending on the polarization of the incident light, the unique optical properties of the bowtie aperture are a result of either the optical waveguide and the coupled surface plasmon polariton modes existing in the bowtie gap or the coupling between the two open arms of the bowtie aperture.

Gain-assisted propagation of electromagnetic energy in subwavelength surface plasmon polariton gap waveguides

The propagation of electromagnetic energy via coupled surface plasmon polariton modes in a metal–insulator–metal heterostructure is analyzed analytically for a core material exhibiting optical gain. It is shown that a sufficiently large gain can completely compensate for the absorption losses due to energy dissipation in the metallic boundaries, enabling long-range transport with a confinement below the diffraction limit for on-chip switching and sensing applications. For a free-space wavelength of 1500nm, lossless propagation in a gold–semiconductor–gold waveguide with a core size of 50nm is predicted for a gain coefficient γ=4830cm−1, comparable to that of semiconductor gain media. The gain requirements decrease with the use of low-index nanocrystal-doped glasses or polymers as core materials.

Photoluminescence emission through thin metal films via coupled surface plasmon–polaritons

We present experimental results showing the variation in photoluminescence from an organic material emitted through a thin metal film as successive dielectric overlayers are added to the far side of the metal. The intensity of the emission from the structure is examined as the surface plasmon–polariton (SPP) modes associated with the two metal surfaces evolve with increasing overlayer thickness from individual to coupled SPP modes. The SPP modes are scattered to produce light by the addition to the metal film of wavelength-scale periodic microstructure. We show that the addition of a dielectric overlayer of an appropriate thickness to the metal film is accompanied by an increase in the intensity of the emission by a factor of 3 over a similar structure with no dielectric overlayer, and by a factor of 50 over a similar planar structure. We show that this increase in emission is mediated via coupled SPP modes.

Coupled surface plasmon-polariton mediated photoluminescencefrom a top-emitting organic light-emitting structure

We report strong photoluminescence from a top-emitting organic light-emitting structure where emission takes place through a thin (55nm) silver film. We show that this emission is mediated via coupled surface plasmon-polariton modes. Our results show that the addition of a dielectric grating to otherwise planar structures, such as surface-emitting organic light-emitting diodes, may offer a way to increase the external efficiency of top-emitting organic light-emitting diodes.