Optical magnet for nanoparticles manipulations based on optical vacuum cleaner concept

The parameters that determine the manipulation of nanoparticles depend on the parameters of the illuminating optical field. This leads to a number of fundamental limitations. For example, the power is limited by the incident wavelength. However, there are several ways to work around these limitations. In this article, we demonstrate that the optical power acts on a nanoparticle placed near a hole made in the shadow surface of a dielectric particle of wavelength dimensions and with a refractive index contrast of 1.8 like an optical magnet, and the nanoparticle is moved into the nanohole. Numerical simulations show that light can be trapped inside a nanohole even when the hole size is only λ/100 and therefore the optical magnet can attract nanoparticles at least of the same size. The use of such an optical magnet is of interest primarily for surface cleaning and biomedical applications.