Optical Pulling Forces Enabled by Hyperbolic Metamaterials.

We propose a novel approach to generating optical pulling forces on a gold nanowire, which are placed inside or above a hyperbolic metamaterial and subjected to plane wave illumination. Two mechanisms are found to induce the optical pulling force, including the concave isofrequency contour of the hyperbolic metamaterial and the excitation of directional surface plasmon polaritons. We systematically study the optical forces under various conditions, including the wavelength, the angle of incidence of light, and the nanowire radius. It is shown that the optical pulling force enabled by hyperbolic metamaterials is broadband and insensitive to the angle of incidence. The mechanisms and results reported here open a new avenue to manipulating nanoscale objects.