Optical Forces in Metal/Dielectric/Metal Fishnet Metamaterials in the Visible Wavelength Regime

The optical force is calculated on a nanoparticle in close proximity to the surface of a fishnet metamaterial based on a metal/dielectric/metal film when illuminated at visible wavelengths. We show that the optical force can be enhanced by the strong magnetic dipole in the fishnet metamaterial. In contrast to other plasmonic nanostructures, which exhibit an attractive force in all regions, our presented structure provides good flexibility in pushing and dragging particular size nanoscale particles at certain distances above the surface of the structure. Therefore, it is suitable for size selection and optical trapping of nanoscale particles at illumination intensities of (1 mW/μm²). At this power level, calculation shows that the optical force can be up to four orders of magnitude larger than the gravitational force for a 100-nm radius nanoparticle.