Remarkable nonlinear optical effect in plasmon-assisted radiation force

Abstract

We study the radiation-induced motive force (radiation force) on a nanoscale particle (NP) nearby metallic nanostructures with considering the optical nonlinear response in the NP. In order to calculate the radiation force, we develop a new method in which one simultaneously solves Maxwell equation for an arbitrary-shaped metallic structure within discrete dipole approximation (DDA), and Liouville equation for a three-level NP. This method enables us to take into account the nonlinear polarization and geometrical information of metallic structure and the NP. It should be noted that the interplay between the metal structure and NP is automatically included because our method self-consistently treats the total electric field and the NP polarization. In addition to the strong enhancement of the radiation force by using the electric field due to the localized surface plasmons (LSPs), it is found that, because of the strong excitation by the LSPs, including nonlinear effect is crucial for some metal structure due to the strong absorption saturation of the NP.