  The recoil optical force that acts on emitters near a surface or waveguide
relies on near-field directionality and conservation of momentum. It features
desirable properties uncommon in optical forces, such as the ability to produce
it via wide-area illumination of vast numbers of particles without the need for
focusing, or being dynamically switchable via the polarization of light.
Unfortunately, these recoil forces are usually very weak and have not been
experimentally observed in small dipolar particles. Some works theoretically
demonstrate orders-of-magnitude enhancement of these forces via complex
nano-structuring involving hyperbolic surfaces or metamaterials, complicating
the fabrication and experimental demonstration. In this work, we theoretically
and numerically show enhancement of the lateral recoil force by simply using
thin metallic films, which support ultra-high-momentum plasmonic modes. The
high-momentum carried by these modes impart a correspondingly large recoil
force on the dipole, enhancing the force by several orders of magnitude in a
remarkably simple geometry, bringing it closer to practical applications.
