Enhanced Optical Forces by Hybrid Long-Range Plasmonic Waveguides

Compared with optical resonant structures, current plasmonic waveguides have the advantage of enhancing optical forces in a broad range of wavelengths, but the enhancement can only be maintained for several dozens of microns at 1.55 μm. Here, a hybrid long-range plasmonic waveguide, consisting of two identical dielectric nanowires symmetrically placed on each side of a thin metal film, is proposed for optical forces. Strong optical coupling between the dielectric waveguide mode and long-range plasmonic mode leads to enhanced optical forces on the dielectric nanowire at low input optical power due to the deep subwavelength optical energy confinement. The enhancement can be maintained for distances of 1~2 orders of magnitude larger than that of previous plasmonic waveguides. The deep subwavelength optical confinement as well as enhanced field gradient also allows efficient trapping of single nanoscale particle, while the smaller propagation loss ensures a much larger trapping region at the same input optical power. The present results enable the potential applications of precisely controlling the positions of dielectric nanowires as well as manipulating a single nanoparticle such as a biomolecule and one quantum dot.