Near- and Far-Field Properties of Plasmonic Oligomers under Radially and Azimuthally Polarized Light Excitation

Abstract

We present a comprehensive experimental and theoretical study on the near- and far-field properties of plasmonic oligomers using radially and azimuthally polarized excitation. These unconventional polarization states are perfectly matched to the high spatial symmetry of the oligomers and thus allow for the excitation of some of the highly symmetric eigenmodes of the structures, which cannot be excited by linearly polarized light. In particular, we study hexamer and heptamer structures and strikingly find very similar optical responses, as well as the absence of a Fano resonance. Furthermore, we investigate the near-field distributions of the oligomers using near-field scanning optical microscopy (NSOM). We observe significantly enhanced near-fields, which arise from efficient excitation of the highly symmetric eigenmodes by the radially and azimuthally polarized light fields. Our study opens up possibilities for tailored light-matter interaction, combining the design freedom of complex plasmonic structures with the remarkable properties of radially and azimuthally polarized light fields.

Excitation dependent Fano-like interference effects in plasmonic silver nanorods

“…The particular amplitude modulation patterns analyzed here are potentially representative of a class of quasi-one-dimensional multipolar modes, and related systems such as modes in kinked wires [25], asymmetric rods [72], and higher-order modes of nanoparticle and nanohole edges [73,74] are suitable candidates for similar hybridization effects. This work also informs further development and evaluation of SPR sensors and devices derived from metal nanorods using other excitations such as shaped near-field excitation [75] or unconventional polarization [76]. Efforts to couple quantum dots [77,78] or absorptive layers [79] in the near field of nanorods will benefit from consideration of local field enhancement at antinodes as a function of location on the nanorod.…”

Selective switching of individual multipole resonances in single dielectric nanoparticles

“…In related studies, even the excitation of a single atom or ion in free space with radially polarized photons was proposed for greatly enhancing the coupling efficiency . All these and many other studies show how advantageous and versatile such polarization‐tailored light beams are for the all‐optical study of nanoscopic systems. Also recent theoretical studies underline these capabilities of such tailored fields .…”

Reconfigurable Near‐field Enhancement with Hybrid Metal‐Dielectric Oligomers

“…For these reasons in our research we choose a seven particle cluster as oligomer, because it can provide data which can be compared not only with plasmonic (see ref. []) but also all‐dielectric oligomer designs (see refs. []).…”

“…Up to now, several solutions were proposed. Namely, it has been demonstrated that the control of excitation polarization can modify the near‐field and the far‐field response of plasmonic oligomer . Another approach for active control of hot spots in plasmonic oligomers proposed recently involves changing the excitation geometry to the opposite one.…”