Similarities and differences for light-induced surface plasmons in one- and two-dimensional symmetrical metallic nanostructures (original) (raw)
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Scientific Reports, 2014
Plasmonic black surfaces formed by two-dimensional arrays of ultra-sharp convex metal grooves, in which the incident radiation is converted into gap surface plasmon polaritons (GSPPs) and subsequently absorbed (via adiabatic nanofocusing), are fabricated and investigated experimentally for gold, nickel, and palladium, using scanning electron microscopy, optical microscopy, and reflection spectroscopy for their characterization. Absolute reflectivity spectra obtained for all fabricated arrays demonstrate very efficient and broadband absorption of unpolarized light exceeding the level of 95%, averaged over the investigated wavelength range of 400-985 nm. The highest averaged absorption level (,97%) is achieved with 250-nm-period arrays in palladium that also has the highest melting temperature (,15526C), promising thereby potential applications for broadband absorption, e.g., within thermophotovoltaics. For one-dimensional arrays, GSPPs are excited only with the electric field polarized perpendicular to the groove orientation, resulting in 94-96% absorption of the appropriately polarized light for the arrays in nickel and palladium while featuring practically flat surface reflectivity spectra for the orthogonal polarization. The largest ratio (,10.7) between averaged reflectivities for orthogonal polarizations is achieved with the groove arrays in palladium, pointing thereby towards applications as broadband and low-dispersion linear polarizers operating in reflection, e.g., within ultra-fast optics.
Excitation of a one-dimensional evanescent wave by conical edge diffraction of surface plasmon
Optics Express, 2011
The experimental observation of a one-dimensional evanescent wave supported by a 90 • metal edge is reported. Through a measurement of in-plane momenta, we clearly demonstrate the dimensional character of this surface wave and show that it is non-radiative in the superstrate. Excitation conditions, lateral extension and polarization properties of this wave are discussed. Finally, we explore the effect of the surrounding dielectric medium and demonstrate that a single edge can sustain distinct excitations.
Band Structures of Two Dimensional Surface Plasmonic Crystals
The dispersion relations and radiation properties of two-dimensional surface plasmonic crystals were studied via the Rigorous Coupled Waved Analysis (Fourier Modal Method). In particular, properties of hexagonal (triangular) lattices with cylindrical protruding pillars (called positive plasmonic crystals) and recessed air holes (negative plasmonic crystals) were investigated for their dispersion relations, mode degeneracies, radiation properties, and plasmonic band gaps. It was found that the optical properties of the crystal are highly dependent on the size and shape of these cylindrical pillars (or holes). Near the Γ point, there are a total of three radiative modes for both positive and negative plasmonic crystals. Two of these three modes couple to both p and s polarized light, whereas one of the modes only couple to p polarized light.
Physical Review E, 2006
In this study, we employ the interfacial operator approach to compute surface plasmon modes as well as band structures ͑including longitudinal modes͒ for plasmonic crystals in one and two dimensions. In particular, we consider the free-electron model for the metal. It is shown that the localized feature of surface plasmon modes can be resolved near the interface by introducing interfacial variables. For a one-dimensional array of metal, convergence of two branches of surface plasmon modes is studied by varying the filling fraction of the metal. For two-dimensional metallic structures, band flattening, band broadening, and plasmonic band gaps are observed and discussed. The highly degenerate nature and infinite number of surface plasmon modes can be explained by employing the Rayleigh quotient for the TE modes. The cutoff behavior in the TM modes is made clear by considering the energy density of the electromagnetic fields. The transverse electric fields, surface charges, and polarization currents are visualized to help understand various properties of surface plasmon modes. Moreover, the effect of plasma frequency and the transition from dispersive metals to perfect conductors are also explored. Finally, the contribution of Drude damping is considered by perturbation analysis.
Nanohole Plasmons in Optically Thin
The optical properties of single nanoholes in optically thin (t=20 nm) gold films on glass have been studied experimentally and theoretically. The measured elastic scattering spectra from the nanoholes exhibit a broad resonance in the red part of the visible spectrum, which is qualitatively similar to localized surface plasmon (LSP) resonances in gold nanodisks. The hole resonance red-shifts with increasing hole diameter (D=60-107 nm), similar to particle LSP resonances. These features could be well reproduced by electrodynamic simulations based on the Boundary Element Method (BEM). Further, the electric field distribution around the resonant nanoholes, obtained from the BEM simulations, exhibits a clear electric dipole pattern. This confirms the assignment of the hole resonance to a dipolar LSP resonance mode. However, in comparison to Au nanodisks of similar size, the hole LSP resonance exhibits a shorter dephasing time (τ). This observation can be understood in terms of an additional decay channel that is dominated by the short wavelength anti-symmetric bound (a b) surface plasmon polariton (SPP) mode of the surrounding Au film. Experimental verification of the LSP-SPP coupling is obtained from near-field scanning optical microscopy images, which exhibit interference fringes due to SPP emission from the hole. The fringe periodicity corresponds to a SPP wavelength of λ a b ≈285 nm, much less than both the free space wavelength λ 0 =633 nm or the wavelength of the more well-known symmetric leaky mode.
Plasmon scattering from single sub-wavelength holes
2012
We map the complex electric fields associated with the scattering of surface plasmon polaritons by single subwavelength holes of different sizes in thick gold films. We identify and quantify the different modes associated with this event, including a radial surface wave with an angularly isotropic amplitude. This wave is shown to arise from the out-of-plane electric dipole induced in the hole, and we quantify the corresponding polarizability, which is in excellent agreement with electromagnetic theory. Time-resolved measurements reveal a time delay of 38 AE 18 fs between the surface plasmon polariton and the radial wave, which we attribute to the interaction with a broad hole resonance.
Microscopic Origin of Surface-Plasmon Radiation in Plasmonic Band-Gap Nanostructures
Physical Review Letters, 2003
We report spatial domain measurements of the damping of surface-plasmon excitations in metal films with periodic nanohole arrays. The measurements reveal a short coherent propagation length of a few m inside nanohole arrays, consistent with delays of about 10 fs in ultrafast transmission experiments. This implies that the transmission spectra of the entire plasmonic band-gap structure are homogeneously broadened by radiative damping of surface-plasmon excitations. We show that a Rayleigh-like scattering of surface plasmons by the periodic hole array is the microscopic origin of this damping, allowing the reradiation rate to be controlled.