Optimization of Near-Field Amplification at Resonant Light Scattering by Nanoparticles

The resonant scattering of a linearly polarized plane EM wave by a spherical nonmagnetic particle is studied within the framework of the exact Mie solution. Separately for metals and for dielectrics, expressions for the parameters of the system are obtained that realize the maximum of the scattered field on the surface of the particle. The solution for metals is found in the form of exact formulas; for dielectrics, an algorithm for finding the coordinates of the maximum is presented. The behaviour of the solution obtained as applied to real substances (Al, Au, GaP) is considered. In the case of metals, with a relatively small dissipation at resonant frequencies, it accurately points to the with an increase in dissipation only vicinity of the maximum is localized. For dielectrics, it is shown that the maxima predicted in the theory turn out to be unattainable due to limitations on the refractive index of the substance, and the reasons for the presence of a maximum, despite the indicated limitation, are investigated. In particular, it was established that the wavelength of the incident radiation and the radius of the particle at the maxima for GaP coincide with the resonance values for the coefficients of the internal field-the assumption from which this study was based. The results obtained in this work provide a guideline for searching for the field maximum upon scattering by other dielectric spherical particles with a relatively small refractive indices.