Light scattering by nanosized systems with different spatial organizations

Abstract

The integrodifferential equation method is used to study the spectrum of a nanoparticle colloid for the example of interaction of three arbitrarily arranged dielectric particles made up of nonresonant atoms (the eigenfrequency of the transition is far from the emission frequency) with incorporated barium atoms in an external optical radiation field. The effect on the light-scattering properties of a nanosphere in the ensemble of its distant "neighbors" is studied; an additional peak associated with them is observed as a frequency close to the resonance for an isolated nanosphere, which under certain conditions has higher intensity than the main peak corresponding to optical near-field resonance in a two-particle system. The dependence of the spectrum of the nanosized system on the geometric structure is studied, and it is shown that very precise tuning of the resonance frequency is possible by varying the angular distribution of the particles.Introduction. In many optical problems connected with emission by microsized and nanosized structures, the problem arises of studying their scattering spectrum, and also identifying the resonance frequencies corresponding to the considered system. In [1], such a problem was solved for the case of metastructural coatings composed of dimers of alkali metals. In [2, 3], clusters were studied that included several tens of interacting atoms. Considerable attention has also been paid to application of such structures in medicine [4-7] (DNA-bound nanoparticles, biomarkers). For this purpose, mainly spherical nanoparticles on the order of 10-30 nm in size have been used, the optical properties of which [8,9] are determined by resonance at the wavelength ≈550 nm. Papers are available that study the light-scattering characteristics of particles of arbitrary shape [10].A large number of papers have also been devoted to study of the interaction between nanoparticles in systems of two or more components. Thus the papers [11,12] study the interaction of a metallic nanosphere with the smooth surface of a semi-infinite medium, which is of significant interest, for example, for optical near-field microscopy. The papers [13,14] study the interaction of a spherical nanoparticle with the surface of an optical medium when island films are present on the surface. This has made it possible to satisfactorily explain the spectral properties of objects observed in [15].We should note that in practically all the indicated papers, the studied structures were considered in the nearest "neighbor" approximation, i.e., neglecting the effect of more distant particles (considering that effect as negligibly small compared with the effect of the surrounding environment). Nevertheless, under certain conditions, we cannot neglect the distant "neighbors", and taking them into account leads to the appearance of additional peaks in the spectrum of the interacting nanoparticles.In this paper, a successive solution of the boundary-value problem of optics for light scattering from some colloid is proposed, taking into...