Mapping the refractive index with single plasmonic nanoantenna

Abstract

As the size of the state-of-the-art optical devices shrinks to nanoscale, the need for tools allowing mapping the local optical properties at deep sub-diffraction resolution increases. Here we demonstrate successful mapping the variations of the refractive index of a smooth dielectric surface by detecting spectral response of a single spherical-shape Ag nanoparticle optically aligned with a supporting optical fiber axicon microlens. We propose and examine various excitation schemes of the plasmonic nanoantenna to provide efficient interaction of its dipolar and quadrupolar modes with the underlying sample surface and to optimize the mapping resolution and sensitivity. Moreover, we demonstrate an lithography-free approach for fabrication of the scanning probe combining the high-quality fiber microaxicon with the Ag spherical nanoparticle atop. Supporting finite-difference time-domain calculations are undertaken to tailor the interaction of the plasmonic nanoantenna and the underlying dielectric substrate upon various excitation conditions demonstrating good agreement with our experimental findings and explaining the obtained results.

Au Nanoparticle-Decorated TiO₂ Nanospheres Produced by Laser Reshaping in Water

“…At the same time, a two-fold increase in the dark-field scattering intensity in the red spectral region (550-750 nm) for a strongly decorated particle is associated with the expected contribution from plasmon-induced resonance scattering of gold nanoparticles located on the TiO2. Red-shifting of scattering band for plasmon-active particles can be explained by their hemispherical shape that provides strong contact with the TiO2 surface, which has a high refractive index [34]. In addition, interacting electromagnetic fields of gold nanoparticles located closer than 30 nm to each other can also contribute to scattering pattern in this wavelength range.…”

Mapping the Refractive Index of Dielectric Surfaces with Spherical Plasmonic Nanoantenna

“…1a) providing the rigorous support to the Ag NP during the scanning process as well as efficient collection of the scattered signal. The optical properties of the FMA are given elsewhere [11,12]. The 100-nm diameter Ag NP supporting the detectable DP and QD modes is produced on the very tip of the FMA using single-pulse laser ablation followed by the ion-beam polishing (Fig.…”

Comparative Simulation of Plasmonic Nanostructures: Optical Response of Periodic Metal Nanostrip and Nanodisk Arrays on Mirror

“…To this end, plasmonic has attracted considerable attention due to its ability to manipulate and control light at the nanoscale, leading to improved performance in sensing, imaging, energy harvesting and other technological applications. [1][2][3][4]. The unique properties of plasmonic structures offer researchers a versatile toolbox for addressing the challenges and opportunities presented in the field of nanophotonics Recently, an alternative plasmonic system known as nanoparticle-on-mirror (NPOM) or filmcoupled nanoparticle system has attracted much attention in the field of plasmonic [4][5][6][7][8][9][10][11].…”

“…[1][2][3][4]. The unique properties of plasmonic structures offer researchers a versatile toolbox for addressing the challenges and opportunities presented in the field of nanophotonics Recently, an alternative plasmonic system known as nanoparticle-on-mirror (NPOM) or filmcoupled nanoparticle system has attracted much attention in the field of plasmonic [4][5][6][7][8][9][10][11]. The key feature of such structures is the coupling of the dipole generated in the nanoparticle with its induced image dipole in the metal layer, which leads to the generation of a hotspot in the gap layer [4,8,12].…”