Spatial and energy characteristics of nanofields in the vicinity of isolated spherical particles

Abstract

Theoretical aspects of the extreme focusing of the optical field to a spatial zone of the subwavelength size are considered in the case of using isolated nanometer- and micrometer-sized spherical particles for this purpose. The intensity of the optical field near the surface of nanospheres of some metals in environments with different values of the refractive index under the exposure to laser radiation in a wide spectral range is calculated numerically. It is shown that as the particle radius decreases, the relative intensity of the optical field of surface plasmons increases and the zone of field nanofocusing shortens. The obtained data are compared with the calculations for gold and aluminum nanoparticles in water. Numerical results illustrating the influence of the shell thickness of composite nanoparticles (dielectric nucleus and metal shell) on the intensity of the optical field of plasmon modes are obtained. The problem of local optical focuses of a transparent microparticle or the so-called photonic nanojets is considered. It is found that varying a micron particle size, its optical properties, and laser radiation parameters allows us to efficiently control the amplitude and spatial characteristics of the photonic nanojet zone.