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.

Femtosecond laser radiation has been used to ablate a gold target in pure deionized water to produce colloidal gold nanoparticles. We report evidence for two different mechanisms of material ablation in the liquid environment, whose relative contributions determine the size distribution of the produced particles. The first mechanism, associated with thermal-free femtosecond ablation, manifests itself at relatively low laser fluences $\text{F<400\hspace{0.17em}}{\mathrm{J/cm}}^2$ and leads to very small (3–10 nm) and almost monodispersed gold colloids. The second one, attributed to the plasma-induced heating and ablation of the target, takes place at high fluences and gives rise to a much larger particle size and broad size distribution. The fabricated nanoparticles exhibit plasmon-related optical absorption peak and are of significance for biosensing applications.