The role of external focusing in spectral enrichment under mid-IR laser filamentation in dielectrics

Coupled plasmonic modes of noble metal nanoparticles are of interest in fields spanning chemistry, physics, materials science, and biology. We systematically investigated the dipole–multipole (D–M) coupling in asymmetric dimers of Au NRs through electromagnetic simulations. First, we calculated the hybridization between Au NR multipole and Au NR dipole in terms of far-field resonances, near-field profiles, and angular scattered radiation profiles at different arrangements. Notably, we found that the parallel aligned D–M plasmonic hybridization leads to asymmetric split resonances that include a multipolar resonance-dominated mode of higher energy and a dipolar resonance-dominated mode of lower energy. Then, we evaluated the “gap space effect” on the strength of D–M hybridization. Furthermore, we studied the dipole’s influence on the D–M coupling via systematically evaluating the optical properties of the dipolar rod’s effects on the hybridized system. Importantly, we discussed the carrier concentration and the damping velocity’s effect on each mode in terms of spectral shifts and near-field enhancement factors, and we found that dipole–octapole (DO) hybridization shows stronger interactions compared to dipole–quadrupole (DQ) hybridization. We hope our work may boost the fundamental understanding of the D–M plasmonic hybridization system and facilitate plasmonic–photonic innovations and nanoplasmonic applications, such as fluorescence imaging, energy storage, biosensors, metamaterials, etc.

Section: Introductionmentioning

confidence: 99%

Parallel Aligned Dipole–Multipole Plasmonic Hybridization

Liu

et al. 2022

“…The localized plasmon resonance (LSPR) of small spherical nanoparticles is primarily dipolar in nature, but additional higher-order harmonic modes (multipoles) can be detected for larger or anisotropic nanoparticles. − In nanorods excited with an incident electric field (E-field) component pointing along the nanorod’s long axis, a standing surface plasmon polariton (SPP) wave is formed by constructive interference between a newly originating surface wave and a longitudinal surface plasmon that travels back and forth along the nanostructure and reflects at the end given a phase shift change of an integer number of 2π. The constructive interference forms standing wave patterns along the nanorod and shows similarities to a guided plasmon of the Fabry–Pérot resonator’s different mode orders. ,, Such multipolar resonances are of fundamental interest, and the near-field profiles and the far-field scattering patterns of multipolar harmonics can be useful in various applications, such as transformation optics, − forensic examination, − plasmonic waveguides, etc.…”

Section: Introductionmentioning

confidence: 99%

Angular Scattered Light Intensity of Dipole–Multipole Plasmonic Hybridization

Wang

2021

The coupled plasmonic modes of noble metal nanoparticles are of interest in fields spanning chemistry, physics, materials science, and biology. We systematically investigated the near- and far-field optical response of a dipole–multipole (D–M) coupled gold nanorod (Au NR) dimer structure. We show that the coupling behavior of D–M resonances leads to redshifted bonding and blueshifted antibonding modes that are analogous to the dipole–dipole coupling observed in the plasmon hybridization framework of Nordlander et al. In particular, the antibonding modes of Au NR dimers are very similar to multipolar resonances of the Au NR monomer of equivalent overall length. These antibonding modes show almost identical far-field plasmon resonance peaks and near-field distribution and also have similar far-field angular radiation profiles with even stronger intensities. We also evaluated Au NR dimer structures of different gap distances in terms of near-field intensities, phase changes, and angular scattering patterns, which exhibit coupling behavior ranging from strongly interacting D–M systems to uncoupled individual elements over a variety of gap distances. Our studies may advance the fundamental understanding of D–M coupled plasmonic systems and pave the path to new opportunities for nanoplasmonic applications, such as fluorescence imaging, energy storage, biosensors, metamaterials, etc.

“…The “hybridization” is achieved by two plasmonic modes being constructively interfered in the near-field, which results in the splitting of their resonance into the “bright” and radiating bonding mode and “dark” and non-radiating antibonding mode. − The split modes represent the symmetric and asymmetric combination of two plasmon resonances. Particularly, the “bright” modes possess “hot spots” of enhanced localized electromagnetic field at the bonding junction, , which have been extensively applied in the practical use of field-enhanced spectroscopy, molecular sensing, , and light harvesting. , On the other hand, the “dark” modes of non-radiative and low scattering loss nature are promising for new applications and opportunities in vast regimes, such as Fano resonance engineering, − transformation optics, − electromagnetically induced transparency, , electromagnetic energy storage, , forensic examination, − plasmonic waveguides, and so forth.…”

Section: Introductionmentioning

confidence: 99%

Near- and Far-Field Optical Properties of Dipole-Multipole Plasmonic Coupled Building Blocks

Liu

et al. 2023

The plasmonic hybridization in the complex nanostructure innovates multiple fields, such as chemistry, physics, materials science, and biology. In this article, we systematically studied the near- and far-field optical properties of building blocks of coupled dipoles or coupled dipoles and multipoles or a multipole in a coupled plasmonic system through numerical simulations. To be specific, the far-field spectrum, near-field phase changes, and angular radiation patterns of plasmonic hybridized structures were calculated. Also, the “gap separation effect” on the strength of plasmonic hybridization was discussed via spectral and near-field evaluation. Additionally, we investigated the coupling between building blocks and different shapes of dipoles through the near- and far-field study. To some extent, our studies have theoretically proven that, compared to the plasmonic coupling among dipoles, the coupling between multipoles and dipoles show mostly comparative and even stronger hybridization in terms of both near- and far-field, which led to the expanded broad range of resonance and stronger localized E-field. We believe that our work may contribute to the fundamental understanding of the plasmonic hybridization system and pave the path for new applications and opportunities in vast regimes of plasmonic-photonic and nanoplasmonic.