Grading plasmonic nanoparticles with light

Abstract

We introduce an approach for fine grading of plasmonic ellipsoidal nanoparticles by two interfering light beams. We consider electrically neutral subwavelength metal nanoparticles whose response is described within the dipole approximation. For the ellipsoidal nanoparticles, we find that their polarizability tensor is strongly dispersive due to the existence of two orthogonal plasmon modes. These modes can be resonantly excited by light and the optical force experienced by particles depends on the ratio of ellipsoid semiaxes. This dependence allows us to spatially separate ellipsoidal particles with different aspect ratio. The eigenfrequencies of plasmons depend on the depolarization factor as well as on the permittivity of the environment and therefore our results can potentially be employed in a wide frequency range including near infrared, visible, and ultraviolet. Show more