Numerical analysis of tip-localized surface plasmon resonances in periodic arrays of gold nanowires with triangular cross section

Abstract

In this contribution, we numerically study the tip enhancement of localized surface plasmons in periodic arrays of gold nanowires with triangular cross section under different illumination configurations. We found that the plasmonic resonance in a single nanowire is excited with a transverse magnetic (TM) plane wave impinging from the substrate at the critical angle, whereas grazing angles are required for the excitation of resonant propagating modes in periodic arrays of triangular-shaped nanowires. Moreover, we found that resonant plasmonic quasi-Bloch modes are efficiently excited with the fundamental TM mode of a dielectric waveguide placed underneath the array. The integrated plasmonic structure allows a strong enhancement of the electromagnetic field at the tip of the nanowires, hence its potential application in the development of new nanophotonic devices.

Photoinduced Temperature Gradients in Sub‐Wavelength Plasmonic Structures: The Thermoplasmonics of Nanocones

“…For each different nanocone height we can point out i) a temperature gradient, as promoted by the thermal hotspot, is associated with an apex resonance, EM hotspot, that effectively localizes the EM power in the apex, ii) while the nanocone first order resonance generally produces the largest near field enhancement, [57] the high-order resonances even though carrying less pronounced near field enhancements (more evident in longer cones) tend to more effectively localize the EM power density in the apex (see also Figure S5, Supporting Information), and iii) a high field enhancement does not necessarily imply a strong temperature gradient, instead, a strong temperature gradient in the nanocone requires the proper combination of high EM power absorption in the apex volume (thus establishing a dominant heat source localized at the apex) with well-defined EM hotspots. Furthermore, by increasing the nanocone height, a red-shift of the apex resonances, evidenced in the electric field enhancement, can be observed [57,59] together with a red-shift of both the apex power peaks and the temperature gradient. Interestingly, an increase of the cone height also determines an increase of the generated temperature gradient, a trend easily understood by recalling that a longer cone means longer distance between the thermal hotspot, located at the cone apex, and the cone base.…”

“…Furthermore, by increasing the nanocone height, a red-shift of the apex resonances, evidenced in the electric field enhancement, can be observed [57,59] together with a red-shift of both the apex power peaks and the temperature gradient. Interestingly, an increase of the cone height also determines an increase of the generated temperature gradient, a trend easily understood by recalling that a longer cone means longer distance between the thermal hotspot, located at the cone apex, and the cone base.…”

Nanowires Integrated to Optical Waveguides

“…This means that plasmonic resonances in metallic nanowires can be excited only if the electric field is perpendicular to the invariant y axis, i. e. with TM polarized light. Thus, the plasmonic chain modes in metallic nanowires will mainly depend on the geometry of their cross section [26][27][28].…”

“…The dispersion curves in the first Brillouin zone are plotted in Figure 13c, where can be observed the light lines of air superstrate (white curve), glass substrate (black curve) and core of the waveguide (green curve). The colored regions correspond to the normalized absorption spectra obtained when illuminating the structure from the substrate with a plane wave and mapped into β ¼ k 0 n sub sin θ inc Λ=π (see reference [28] for a detailed explanation). The blue triangles curve in the guided region correspond to the fundamental TM 0 photonic mode of the isolated waveguide.…”

Coupled localized surface plasmon resonances in periodic arrays of gold nanowires on ion-exchange waveguide technology

“…In this sense, the integration of plasmonic arrays of metallic nanowires with dielectric optical waveguides becomes an attractive approach. These hybrid photonic-plasmonic systems provide an efficient excitation of coupled LSPRs in chains of MNPs [15] and metallic nanowires with different cross sections [16,17]. For applications across the visible spectrum, different platforms for photonic integrated circuits have been proposed such as lithium niobate [18] and silicon nitride [19] waveguides.…”