Light scattering and surface plasmons on small spherical particles

Light scattering by small particles has a long and interesting history in physics. Nonetheless, it continues to surprise with new insights and applications. This includes new discoveries, such as novel plasmonic effects, as well as exciting theoretical and experimental developments such as optical trapping, anomalous light scattering, optical tweezers, nanospasers, and novel aspects and realizations of Fano resonances. These have led to important new applications, including several ones in the biomedical area and in sensing techniques at the single-molecule level. There are additionally many potential future applications in optical devices and solar energy technologies. Here we review the fundamental aspects of light scattering by small spherical particles, emphasizing the phenomenological treatments and new developments in this field. The interaction of light with small spherical particles has long been a topic of interest to researchers. Indeed, understanding many natural phenomena, including rainbows and the solar corona, requires knowledge of how light behaves in such circumstances. Xiaofeng Fan and co-workers from Jilin University in China and Oak Ridge National Laboratory in the USA have now reviewed the physics and applications that arise during the interaction of light with small spherical particles. The researchers describe how Mie theory can be used to describe optical scattering by small dielectric particles, and, in the case of metallic particles, how light excites surface plasmons to generate an optical response featuring asymmetric Fano resonances. In the special case when metallic particles are surrounded by an optical gain medium, plasmons can be amplified; the resulting device is known as a ‘spaser’.