Optical force propelled by metamaterial surface waves excitation: pushing and tractor beam sources

Abstract

Theoretical research on opto–mechanical interactions at sub–wavelength levels usingsurface waves (SWs) excitation has a great impact in both the academic knowledge and practicalrealm. In this letter we have revealed that the dynamic characteristics of the SWs excitedalong a metamaterial boundary, such as its forward or backward propagation nature, provide adirect demonstration about the direction of action of the optical force exerted on a dielectricnano–particle. In particular, by using a rigorous electromagnetic formalism based in the secondGreen identity, we have modeled the scattering problem of a Gaussian beam impinging ona metamaterial plane surface with a sub–wavelength localized defect. We have shown thatdepending on the nature of the excited SW, dielectric nano–particles placed near the surface canbe pushed away or towards the localized defect. We believe that this work unveils the potentialimplementation of sub–wavelength defects as sources of pushing or pulling optical forces.