Transforming optical forces

We show how transformation optics can enhance optical gradient forces between two optical waveguides by several orders of magnitude. The technique is based on a coordinate transformation that alters the perceived distance between the waveguides. This transformation can be implemented using single-negative metamaterial thin films. The process is remarkably robust to the dissipative loss normally observed in metamaterials. Therefore, our results provide an alternative way to enhance optical forces in nanophotonic actuation systems and may be combined with existing resonator-based enhancement methods to produce optical gradient forces with unprecedented amplitude [Phys. Rev. Lett. 110, 057401 (2013)].