title: Optical forces in nanorod metamaterial.
abstract: Optomechanical manipulation of micro and nano-scale objects with laser beams finds use in a large span of multidisciplinary applications. Auxiliary nanostructuring could substantially improve performances of classical optical tweezers by means of spatial localization of objects and intensity required for trapping. Here we investigate a three-dimensional nanorod metamaterial platform, serving as an auxiliary tool for the optical manipulation, able to support and control near-field interactions and generate both steep and flat optical potential profiles. It was shown that the 'topological transition' from the elliptic to hyperbolic dispersion regime of the metamaterial, usually having a significant impact on various light-matter interaction processes, does not strongly affect the distribution of optical forces in the metamaterial. This effect is explained by the predominant near-fields contributions of the nanostructure to optomechanical interactions. Semi-analytical model, approximating the finite size nanoparticle by a point dipole and neglecting the mutual re-scattering between the particle and nanorod array, was found to be in a good agreement with full-wave numerical simulation. In-plane (perpendicular to the rods) trapping regime, saddle equilibrium points and optical puling forces (directed along the rods towards the light source), acting on a particle situated inside or at the nearby the metamaterial, were found.
authors.affiliation: ITMO University, St. Petersburg, 197101, Russia.|Ioffe Institute, St. Petersburg, 194021, Russia.|Peter the Great St. Petersburg Polytechnic University, St. Petersburg, 195251, Russia.
authors.forename: Andrey A
authors.initials: AA
authors.lastname: Bogdanov
authors.affiliation: ITMO University, St. Petersburg, 197101, Russia.
authors.forename: Alexander S
authors.initials: AS
authors.lastname: Shalin
authors.affiliation: School of Electrical Engineering, Tel Aviv University, Tel Aviv, 69978, Israel.
authors.forename: Pavel
authors.initials: P
authors.lastname: Ginzburg