Double-layered nanoparticle stacks for spectro-electrochemical applications

Plasmonic Surface Lattice Resonances: A Review of Properties and Applications

When metal nanoparticles are arranged in an ordered array, they may scatter light to produce diffracted waves. If one of the diffracted waves then propagates in the plane of the array, it may couple the localized plasmon resonances associated with individual nanoparticles together, leading to an exciting phenomenon, the drastic narrowing of plasmon resonances, down to 1–2 nm in spectral width. This presents a dramatic improvement compared to a typical single particle resonance line width of >80 nm. The very high quality factors of these diffractively coupled plasmon resonances, often referred to as plasmonic surface lattice resonances, and related effects have made this topic a very active and exciting field for fundamental research, and increasingly, these resonances have been investigated for their potential in the development of practical devices for communications, optoelectronics, photovoltaics, data storage, biosensing, and other applications. In the present review article, we describe the basic physical principles and properties of plasmonic surface lattice resonances: the width and quality of the resonances, singularities of the light phase, electric field enhancement, etc. We pay special attention to the conditions of their excitation in different experimental architectures by considering the following: in-plane and out-of-plane polarizations of the incident light, symmetric and asymmetric optical (refractive index) environments, the presence of substrate conductivity, and the presence of an active or magnetic medium. Finally, we review recent progress in applications of plasmonic surface lattice resonances in various fields.

Role of surface plasmon resonant modes in anomalous terahertz transmission through double-layer metal loop arrays

A three-layer construction was proposed to induce anomalous transmission response for a normal incidence of terahertz (THz) wave. This structure was composed of a dielectric layer of quartz and two metallic layers, which were deposited on the two surfaces of quartz and patterned the same periodic arrays of subwavelength air circular loop. Based on comparative analyses of dispersion relations of both the structure and its partial structures, propagating surface plasmon and localized surface plasmon principally dominated the lower and higher resonant peaks appearing in the calculated transmittance spectrum, respectively. A sample was fabricated by laser technology for experiment and the measured THz transmission showed a good agreement with simulation, providing reference for potential applications.

Double-layered nanoparticle stacks for surface enhanced infrared absorption spectroscopy

We demonstrate that double-layered stacks of gold and insulator nanoparticles arranged on a flat gold surface dramatically enhance the sensitivity in absorption infrared microscopy. Through morphological variations of the nanoparticles, the frequency of the plasmon resonances can be tuned to match the frequency of the molecular vibration in the mid-infrared region. The results show that the nanostructures enhance the absorption signal of the molecules by a factor of up to ~2.2 × 10(6), while preserving their characteristic line-shape remarkably well.