The Bottom-Up Approach toward Artificial Optical Magnetism in Metastructures

Abstract

The generation of artificial optical magnetism (AOM) in engineered composites has been the major concept that led to the emergence of the field of metamaterials at the turn of the millennium. Indeed, the proven possibility to manipulate the magnetic permeability of materials at microwave frequencies induced a considerable excitement in the scientific community as it opened the way to the design of unprecedented tools and devices for the control of light propagation. Extensions to higher frequencies of IR and visible light were soon proposed and tested by downsizing the artificial structures. The fabrication of negative index materials, optical cloaks or hyper-lenses seemed within reach. Two decades later, and after considerable research efforts, the applications of the AOM are still scarce and the concept seems to face a number of fundamental physical limits. We review in this chapter the state-of-the-art of the bottom-up approach whereby nanochemistry and colloidal physics are used to engineer hybrid metastructures exhibiting AOM in visible light or near IR.

Gain-driven singular resonances in active core-shell and nano-shell plasmonic particles

“…Moreover, metallic nanostructures with gain elements are nanoscale sources of strong optical fields; this intriguing feature, culminating in the conception of the SPASER, widened their potential applicability to nanoscale lithography, probing, microscopy and more [20][21][22][23]. In the zoo of proposed nanostructures, a prominent role is played by core-shell and nano-shell nanoparticles, for they are controllable and stable plasmonic structures including all features needed for diverse optoelectronic applications [24][25][26][27], and they are obtainable in large numbers via nanochemical synthesis [28,29].…”

Bottom-up synthesis of meta-atoms as building blocks in self-assembled metamaterials: recent advances and perspectives

“…A major focus of this bottom-up approach has been the generation of artificial optical magnetism [12,13]. Gomez-Graña et al produced a bulk self-assembled three-dimensional isotropic material that exhibited a magnetic response at visible frequencies [14].…”

Colloidal Self-Assembly of Silver Nanoparticle Clusters for Optical Metasurfaces

“…These methods usually yield very large amounts of particles of controlled average sizes and have been proposed for the fabrication − and the assembly − of meta-atoms. They can provide particles of complex structures, e.g., composed of subparticles with a specific arrangement, exhibiting optical scattering and absorption properties that would otherwise be unattainable with homogeneous and simple shaped particles. ,− Although the polydispersity of the meta-atoms assembled with such methods is notably higher than those of top-down fabrication, the sheer number of meta-atoms synthesized in a single batch makes it possible to produce surfaces that are potentially orders of magnitude larger than what is typically achievable by top-down schemes. Furthermore, this also means that there is usually room for particle sorting to increase monodispersity without worrying about the affordability of losing meta-atoms in the process.…”

“…Several types of such devices were successfully produced like metallic dimers, , U-shaped imprints, or fishnet structures, , for which artificial optical magnetism was reported. In order to minimize optical losses, top-down technologies were also applied to silicon-based systems operating in the near infrared. , Self-assembly methods have typically contributed to this endeavor by fabricating subwavelength structured composite particles and materials that harbor strong optical magnetism. ,,,, Today, it is clear that artificial optical magnetism is an essential, if not necessary, ingredient for the development of metasurfaces.…”