Enhancing plasmonic response by scattering of a beam under spherical aberration

Abstract

The plasmonic response of a spherically symmetric nanoparticle is theoretically analysed using the Mie theory and multipole expansion for a tightly focused beam under the spherical aberration and defocusing. It is observed that the spherical aberrations present in the system amend the absorption and scattering efficiency of the nanoparticles, and the electromagnetic field around the nanoparticle. An enhancement in the near-field intensity appears due to excitement of plasmons on the surface of a nanoparticle and this is further increased for a beam under spherical aberration. In contrast to the aberration free case where radial component was dominating in the near field intensity enhancement, presence of spherical aberration in the focusing system significantly enhances the contribution of the tangential component in addition to the radial component. Defocusing aberration is also introduced to compensate the effect of spherical aberration and results are presented for the balancing condition. © 2024