Significant Near-Field Enhancement over Large Volumes around Metal Nanorods via Strong Coupling of Surface Lattice Resonances and Fabry–Pérot Resonance

Abstract

Metal nanoparticles supporting plasmons are widely used to enhance electromagnetic fields, resulting in strong light–matter interactions at the nanoscale in a diverse range of applications. Recently, it has been shown that when metal nanorods are periodically arranged with proper lattice periods, surface lattice resonances (SLRs) can be excited and near fields can be greatly enhanced over extended volumes. In this work, we report significant near field enhancement over even larger volumes by placing the metal nanorod array within a Fabry–Pérot (F-P) microcavity. Simulation results show that by taking advantage of strong coupling between the SLR and the photonic F-P resonances, the electric field intensity of the bonding split mode can be enhanced by up to 1935 times, which is about three times of the enhancement of the SLR, and the greatly enhanced field can extend over most of the F-P microcavity. We further show that the F-P resonances of both odd and even orders can strongly couple to the SLR by varying the nanorods position from the middle of the microcavity. We expect that the proposed plasmonic-photonic coupling system will find promising applications in nanolasers, nonlinear optics and sensing.

Control, Modulation, and Analytical Descriptions of Vibrational Strong Coupling

“…The form factor of a parallel plane cavity accommodates incorporation of additional resonators of various sorts. 72 One such work, 73 by Hertzog et al, employs simultaneous coupling between an array of Au nanorod resonators, a FP cavity, and an ensemble of molecules contained within the nanorod-cavity device. Alone, the nanorod arrays exhibit broad resonances in the mid-infrared with radiatively limited line widths spanning 600−1100 cm −1 .…”

Plasmonic Coupled Modes in a Metal–Dielectric Periodic Nanostructure

“…This behavior arises due to the enhanced near-field coupling between the metal film and the nanoblocks when the gap thickness is much smaller than the wavelength of the incident light. This effect can be understood in the context of a Fabry–Perot resonator [ 13 ], which involves multiple reflections between metal surfaces and results in the generation of transmission peaks and reflectance dips in the system’s spectral response due to interference phenomena between the reflected waves. However, it is important to note that the GSP resonance relies on the interference of surface waves, rather than the interference of waves between two mirrors as in the case of a Fabry–Perot resonator.…”

“…The detailed mechanism underlying the transition from Fabry–Perot resonance to GSPR falls outside the scope of the present study. Interested readers are referred to relevant literature, including [ 13 ] and references therein. On the other hand, the dips with the smallest bandwidth, as shown in Figure 2 , exhibit a nearly linear dispersion in wavelength when the lattice period is varied.…”

“…Periodic arrays of plasmonic nanoparticles [ 1 , 2 , 3 ] are essential structures in nanoscience and nanotechnology and, therefore, a deep understanding of their fundamental properties and applications is necessary for the development of advanced nanophotonic circuitry [ 4 , 5 , 6 ]. Unlike the metal–dielectric interface, which only supports well-known surface plasmon polaritons (SPPs) [ 7 , 8 ] and localized surface plasmons (LSPs) [ 9 , 10 ], such arrays can couple modes between the LSP of a single constituent scatterer (typically a nanoparticle) and the diffractive modes of the lattice structure, resulting in particle–lattice field enhancements larger than those of the same number of isolated elements [ 11 , 12 , 13 ]. Such coupled electromagnetic modes are referred to as surface lattice resonances (SLRs) [ 2 , 14 ], and their optical properties are highly dependent on the lattice periodicity, scatterer morphology, nature of the metal, and the refractive index of the environment.…”