Characteristics of Photonic Nanojet Formation on a Spherical Cluster of Dielectric Nanoparticles.

Results of numerical simulations of optical radiation focusing by a cluster of identical nanospheres close packed into a spherical volume (a "metaparticle") are presented. Parameters of the focal region (intensity and longitudinal and transverse sizes) formed by metaparticles with different internal structure are calculated. It is shown that the problem of optical radiation focusing by a spherical cluster of nanoparticles can be reduced in certain cases to the problem of light focusing by a homogeneous spherical particle with an effective refractive index derived from the effective medium theory. Moreover, certain spherical cluster topologies make it possible to improve optical focusing in the near-field region, in particular, to increase the peak intensity or enhance its spatial localization. [ABSTRACT FROM AUTHOR]