Pulling a Structure With Laser Light by Regulation of Resonances

The physical basis for pulling a passive nanostructured surface with light is presented and supported with numerical simulations of fields and force density in the material. A net optical force in the direction opposite to that of the incident light is described for a structure composed of a periodic array of slots in a gold film on a dielectric membrane and with single-plane-wave illumination. The force density due to a plasmon surface wave resonance on the back dominates and results in the structure being pulled towards the incident light. Previous pulling concepts relied on structuring an incident beam to influence motion of a small particle. In this case, by contrast, the structure is regulating the scattered field and hence influencing the net force. In addition, an example metal-dielectric structure is presented that allows pushing or pulling, depending on wavelength and whether the surface wave on the front or the back dominates, respectively. Such interplay between material, structure at the nanometer-scale, and optical force should have substantial consequences in applications that include all-optical communication, remote actuation, propulsion, and biophysics.