Coupling and hybridization of surface plasmon polaritons (SPPs) in metal nanostructures

ABSTRACT:Surface plasmon polaritons (SPPs), which are coupled excitations of electrons bound to a metal-dielectric interface, show great potential for application in future nanoscale photonic systems due to the strong field confinement at the nanoscale, intensive local field enhancement, and interplay between strongly localized and propagating SPPs. The fabrication of sufficiently smooth metal surface with nanoscale feature size is crucial for SPPs to have practical applications. A template stripping (ST) method combined with PMMA as a template was successfully developed to create extraordinarily smooth metal nanostructures with a desirable feature size and morphology for plasmonics and metamaterials. The advantages of this method, including the high resolution, precipitous top-to bottom profile with a high aspect ratio, and three-dimensional characteristics, make it very suitable for the fabrication of plasmonic structures. By using this ST method, boxing ring-shaped nanocavities have been fabricated and the confined modes of surface plasmon polaritons in these nanocavities have been investigated and imaged by using cathodoluminescence (CL) spectroscopy, which has been turned out to be a powerful means to characterize the resonant SPPs modes confined in metal nanocavities [1∼5] . The mode of the out-of-plane field components of surface plasmon polaritons dominates the experimental mode patterns, indicating that the electron beam locally excites the out-of-plane field component of surface plasmon polaritons. Quality factors can be directly acquired from the spectra induced by the ultrasmooth surface of the cavity and the high reflectivity of the silver (Ag) reflectors. Because of its three-dimensional confined characteristics and the omnidirectional reflectors, the nanocavity exhibits a small modal volume, small total volume, rich resonant modes, and flexibility in mode control. Numerous applications, such as plasmonic filter, nanolaser, and efficient light-emitting devices, can be expected to arise from these developments.

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Propagation length enhancement of surface plasmon polaritons in gold nano-/micro-waveguides by the interference with photonic modes in the surrounding active dielectrics

Nanophotonics ◽

10.1515/nanoph-2016-0166 ◽

2017 ◽

Vol 6 (5) ◽

pp. 1109-1120 ◽

Cited By ~ 8

Author(s):

Isaac Suárez ◽

Albert Ferrando ◽

Jose Marques-Hueso ◽

Antonio Díez ◽

Rafael Abargues ◽

...

Keyword(s):

Surface Plasmon ◽

Surface Plasmon Polaritons ◽

Laser Energy ◽

Strong Electric Field ◽

Light Signal ◽

Metal Nanostructures ◽

Propagation Length ◽

Simultaneous Excitation ◽

Visible Wavelengths ◽

Plasmon Polaritons

AbstractIn this work, the unique optical properties of surface plasmon polaritons (SPPs), i.e. subwavelength confinement or strong electric field concentration, are exploited to demonstrate the propagation of light signal at 600 nm along distances in the range from 17 to 150 μm for Au nanostripes 500 nm down to 100 nm wide (30 nm of height), respectively, both theoretically and experimentally. A low power laser is coupled into an optical fiber tip that is used to locally excite the photoluminescence of colloidal quantum dots (QDs) dispersed in their surroundings. Emitted light from these QDs is generating the SPPs that propagate along the metal waveguides. Then, the above-referred propagation lengths were directly extracted from this novel experimental technique by studying the intensity of light decoupled at the output edge of the waveguide. Furthermore, an enhancement of the propagation length up to 0.4 mm is measured for the 500-nm-wide metal nanostripe, for which this effect is maximum. For this purpose, a simultaneous excitation of the same QDs dispersed in poly(methyl methacrylate) waveguides integrated with the metal nanostructures is performed by end-fire coupling an excitation laser energy as low as 1 KW/cm2. The proposed mechanism to explain such enhancement is a non-linear interference effect between dielectric and plasmonic (super)modes propagating in the metal-dielectric structure, which can be apparently seen as an effective amplification or compensation effect of the gain material (QDs) over the SPPs, as previously reported in literature. The proposed system and the method to create propagating SPPs in metal waveguides can be of interest for the application field of sensors and optical communications at visible wavelengths, among other applications, using plasmonic interconnects to reduce the dimensions of photonic chips.

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