Mie scattering of tightly focused beams by a core-shell nanoparticle

Abstract

Scattering of tightly focused beams by a coated nanosphere is examined using Mie theory and multipole expansion approach. Interaction of a coated nanoparticle (NP) is considered with three different beams namely, plane wave and tightly focused linearly and radially polarized beams. Tight focusing is realized using the Richards-Wolf integral, and their interaction with a plasmon active silver coated gold (Au@Ag) NP is investigated for a fixed core (Au) and outer shell (Ag). The near-field intensity enhancement is analyzed by using scattering coefficients for a spherically symmetric homogeneous coated sphere. An appreciable increase in enhancement factor is observed for Au@Ag NP in a silicon medium with a tightly focused radially polarized beam. Variation in enhancement factor is observed by changing the thickness of outer Ag coating around the Au core. © 2024 Elsevier B.V.