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

Abstract

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