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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]

Spatial resolution of conventional optics, which is necessary for nondestructive trapping of microobjects, is limited by diffraction to a value equal to half of the radiation wavelength. Despite this limitation, use of optical methods is one of the main directions in biological and biomedical researches because only these methods have a minimal impact on living organisms. The rapid advance in this area is largely owing to the development of new optical technologies and the considerable advance in mesoscale photonics, which has allowed researchers to develop techniques for controlling structured beams for optical traps. In this work, we consider some recent trends in the field of optical manipulation based on mesoscale dielectric particles. [ABSTRACT FROM AUTHOR]

The results of theoretical studies of spatially localized near-field light structures (photonic nanojets) formed when laser radiation is scattered on a meta-surface having the form of an ordered single-layer assembly of dielectric microparticles (spheres, cones) embedded in a transparent matrix (silicone film) are presented. The behavior of the main parameters of the localized light structures (length, width, and peak intensity) under the effects of light fields of neighboring microparticles is thoroughly analyzed by using computational electrodynamics to solve Maxwell's equations with the finite-difference time-domain method (FDTD). It is ascertained that the main factors which affect the parameters of photonic nanojets under study are the spatial orientation of the microcones and the depth of their immersion in the silicone matrix. It is shown that several spatial configurations of the microassembly of the cones allow the creation of an ensemble of photonic nanojets with specific parameters, which are unattainable for isolated microcones. Ordered clusters of spherical particles have an advantage in terms of a comprehensive assessment of the parameters of photonic nanojets. [ABSTRACT FROM AUTHOR]

The effect of photonic nanojets (PNJ) in the scattering near field nearby the surface of dielectric axisymmetric microparticles (hemisphere, axicon, and combined particles) under optical illumination is theoretically considered. Key PNJ parameters (length, width, and peak intensity) are calculated using the discrete-dipole approximation; the dependence of these parameters on the geometric shape of microparticles is analyzed. We show that the use of a special type of combined transparent particle, which consists of an axicon and two attached hemispheres, can produce ultralocalized light fluxes with a peak intensity which considerably exceeds the corresponding values for simple particles (hemisphere and axicon). [ABSTRACT FROM AUTHOR]

Optical field parameters in a 'photonic nanojet' formed near surfaces of dielectric spherical microparticles illuminated by a focused laser beam are studied theoretically. The influence of the beam waist on 'photonic nanojet' parameters (length, width, and intensity) is analyzed. [ABSTRACT FROM AUTHOR]