Abstract
We study the hybridized plasmonic-photonic modes supported by two-dimensional arrays of metallic nanoparticles coupled to light-emitting optical waveguides. Localized surface plasmon polaritons in the metallic nanoparticles can couple to guided modes in the underlying waveguide, forming quasi-guided hybrid modes, or to diffracted orders in the plane of the array, forming surface lattice resonances. We consider three kinds of samples: one sustains quasi-guided modes only, another sustains surface lattice resonances only, and a third sample sustains both modes. This third sample constitutes the first demonstration of simultaneous coupling of localized surface plasmons to guided modes and diffracted orders. The dispersive properties of the modes in the samples are investigated through light extinction and emission spectroscopy. We elucidate the conditions that lead to the coexistence of surface lattice resonances and quasi-guided hybrid modes, and assess their potential for enhancing the luminescence of emitters embedded in the coupled waveguide. We find the largest increase in emission intensity for the surface lattice resonances, reaching up to a factor of 20.
Highlights
Plasmonic nanostructures are currently being intensively investigated
We study the hybridized plasmonic-photonic modes supported by two-dimensional arrays of metallic nanoparticles coupled to light-emitting optical waveguides
The intensity in the yttrium aluminium garnet (YAG):Ce layer is stronger in Fig. 6(e) than in 6(d), which is in agreement with the experimental results displayed in Fig. 5 where the strongest enhancement was achieved for the surface lattice resonances (SLRs)
Summary
Plasmonic nanostructures are currently being intensively investigated. The reason for this pronounced interest is their very large polarizability due to localized surface plasmon resonances (LSPRs), which allows to enhance light-matter interactions [1,2,3,4,5,6,7]. Of particular interest are periodic arrays of metallic nanoparticles with a lattice constant comparable to the wavelength of light In these arrays, the radiative coupling can be enhanced by surface or guided modes. SLRs are favored when the array of nanoparticles is embedded in an homogeneous dielectric [27] and for large nanoparticles [27, 28] Both quasi-guided modes and SLRs have been extensively studied, they have never simultaneously reported in a single sample because of the different conditions to support them: Quasi-guided modes need a waveguide that has a higher refractive index than the surrounding, while SLRs are favored when the medium surrounding the array is homogeneous.
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